Handle APB frequency change (#2250)

* Add APB change callbacks and move cpu code to own file

* Properly set esp_timer and FreeRTOS tick dividers

* Improve updated devisors

* No need to update REF_TICK yet

* Add initial handling for UART baud change

* fix uartWriteBuf and uartDetectBaudrate

* trigger callbacks even when APB did not change

* toggle UART ISR on CPU change

* add XTAL freq getter and add cpu freq validation

* Support CPU frequency changes in I2C (#2287)

**esp32-hal-i2c.c**
* add callback for cpu frequency changes
* adjust fifo thresholds based on cpu frequency and i2c bus frequency
* reduce i2c bus frequency if differential is too small
**Wire.h**
* version to 1.1.0

* Implement clock change for the other peripherals

* remove bad CPU clock values from the menu

* Add note to CPU freqs that support WiFi and BT

cores/esp32/esp32-hal-cpu.h

@@ -0,0 +1,48 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _ESP32_HAL_CPU_H_
+#define _ESP32_HAL_CPU_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+typedef enum { APB_BEFORE_CHANGE, APB_AFTER_CHANGE } apb_change_ev_t;
+
+typedef void (* apb_change_cb_t)(void * arg, apb_change_ev_t ev_type, uint32_t old_apb, uint32_t new_apb);
+
+bool addApbChangeCallback(void * arg, apb_change_cb_t cb);
+bool removeApbChangeCallback(void * arg, apb_change_cb_t cb);
+
+//function takes the following frequencies as valid values:
+//  240, 160, 80    <<< For all XTAL types
+//  40, 20, 10      <<< For 40MHz XTAL
+//  26, 13          <<< For 26MHz XTAL
+//  24, 12          <<< For 24MHz XTAL
+bool setCpuFrequencyMhz(uint32_t cpu_freq_mhz);
+
+uint32_t getCpuFrequencyMhz();  // In MHz
+uint32_t getXtalFrequencyMhz(); // In MHz
+uint32_t getApbFrequency();     // In Hz
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _ESP32_HAL_CPU_H_ */