make bootloader_support support esp32s2beta

components/bootloader_support/include/bootloader_clock.h

@@ -19,3 +19,7 @@
  * Called by bootloader, or by the app if the bootloader version is old (pre v2.1).
  */
 void bootloader_clock_configure(void);
+
+/** @brief Return the rated maximum frequency of this chip
+ */
+int bootloader_clock_get_rated_freq_mhz(void);