cmake: Add explicit dependency on esp_netif

esp_netif component is a private requeirements for some freemodbus
sources. This works without declaring a depencency, since esp_netif is
implicitely dependent on esp_event. This will be cleaned up in IDF v5.0.
This change makes the depencency explicit.

CMakeLists.txt

@@ -69,4 +69,5 @@ endif()
 idf_component_register(SRCS "${srcs}"
                     INCLUDE_DIRS "${include_dirs}"
                     PRIV_INCLUDE_DIRS "${priv_include_dirs}"
-                    REQUIRES ${requires})
+                    REQUIRES ${requires}
+                    PRIV_REQUIRES esp_netif)