feat(usb): Add usb_host_lib_set_root_port_power()

This commit adds the usb_host_lib_set_root_port_power() function. This provides
a public API for users to power the root port OFF or ON at runtime, thus trigger
a disconnection or allow connections respectively.

In addition, the usb_host_config_t.root_port_unpowered install configuration is
provided to allow users to install the USB Host Library without automatically
powering ON the root port.

components/usb/include/usb/usb_host.h

@@ -101,10 +101,13 @@ typedef void (*usb_host_client_event_cb_t)(const usb_host_client_event_msg_t *ev
  * Configuration structure of the USB Host Library. Provided in the usb_host_install() function
  */
 typedef struct {
-    bool skip_phy_setup;        /**< If set, the USB Host Library will not configure the USB PHY thus allowing the user
+    bool skip_phy_setup;                        /**< If set, the USB Host Library will not configure the USB PHY thus allowing
-                                     to manually configure the USB PHY before calling usb_host_install(). Users should
+                                                     the user to manually configure the USB PHY before calling usb_host_install().
-                                     set this if they want to use an external USB PHY. Otherwise, the USB Host Library
+                                                     Users should set this if they want to use an external USB PHY. Otherwise,
-                                     will automatically configure the internal USB PHY */
+                                                     the USB Host Library will automatically configure the internal USB PHY */
+    bool root_port_unpowered;                   /**< If set, the USB Host Library will not power on the root port on installation.
+                                                     This allows users to power on the root port manually by calling
+                                                     usb_host_lib_set_root_port_power(). */
     int intr_flags;                             /**< Interrupt flags for the underlying ISR used by the USB Host stack */
     usb_host_enum_filter_cb_t enum_filter_cb;   /**< Enumeration filter callback. Enable CONFIG_USB_HOST_ENABLE_ENUM_FILTER_CALLBACK
                                                      to use this feature. Set to NULL otherwise. */
@@ -187,6 +190,21 @@ esp_err_t usb_host_lib_unblock(void);
  */
 esp_err_t usb_host_lib_info(usb_host_lib_info_t *info_ret);
 
+/**
+ * @brief Power the root port ON or OFF
+ *
+ * - Powering ON the root port will allow device connections to occur
+ * - Powering OFF the root port will disconnect all devices downstream off the root port and prevent
+ *   any further device connections.
+ *
+ * @note If 'usb_host_config_t.root_port_unpowered' was set on USB Host Library installation, users must call this
+ *       function to power ON the root port before any device connections can occur.
+ *
+ * @param enable True to power the root port ON, false to power OFF
+ * @return esp_err_t
+ */
+esp_err_t usb_host_lib_set_root_port_power(bool enable);
+
 // ------------------------------------------------ Client Functions ---------------------------------------------------
 
 /**

components/usb/usb_host.c

@@ -540,8 +540,11 @@ esp_err_t usb_host_install(const usb_host_config_t *config)
     p_host_lib_obj = host_lib_obj;
     HOST_EXIT_CRITICAL();
 
+    if (!config->root_port_unpowered) {
         // Start the root hub
         ESP_ERROR_CHECK(hub_root_start());
+    }
+
     ret = ESP_OK;
     return ret;
 
@@ -694,6 +697,18 @@ esp_err_t usb_host_lib_info(usb_host_lib_info_t *info_ret)
     return ESP_OK;
 }
 
+esp_err_t usb_host_lib_set_root_port_power(bool enable)
+{
+    esp_err_t ret;
+    if (enable) {
+        ret = hub_root_start();
+    } else {
+        ret = hub_root_stop();
+    }
+
+    return ret;
+}
+
 // ------------------------------------------------ Client Functions ---------------------------------------------------
 
 // ----------------------- Private -------------------------