esp32: add get idf version api

components/esp32/include/esp_system.h

@@ -124,7 +124,12 @@ esp_err_t system_efuse_read_mac(uint8_t mac[6]) __attribute__ ((deprecated));
  */
 const char* system_get_sdk_version(void)  __attribute__ ((deprecated));
 
-
+/**
+ * Get IDF version
+ *
+ * @return constant string from IDF_VER
+ */
+const char* esp_get_idf_version(void);
 
 #ifdef __cplusplus
 }

components/esp32/system_api.c

@@ -179,4 +179,8 @@ const char* system_get_sdk_version(void)
     return "master";
 }
 
+const char* esp_get_idf_version(void)
+{
+    return IDF_VER;
+}