esp32/boards: Split out CPU frequency config, make 160MHz the default.

Remove the 240MHz CPU config option from sdkconfig.base and create a new
sdkconfig.240mhz file for those boards that want to use 240MHz on boot.

The default CPU frequency is now 160MHz (was 240MHz), to align with the ESP
IDF and support more boards (eg those with D2WD chips).

Fixes issue #5169.

ports/esp32/boards/TINYPICO/mpconfigboard.mk

@@ -1,5 +1,6 @@
 FLASH_FREQ = 80m
 
 SDKCONFIG += boards/sdkconfig.base
+SDKCONFIG += boards/sdkconfig.240mhz
 SDKCONFIG += boards/sdkconfig.spiram
 SDKCONFIG += boards/TINYPICO/sdkconfig.board

ports/esp32/boards/sdkconfig.240mhz

@@ -0,0 +1,5 @@
+# MicroPython on ESP32, ESP IDF configuration with 240MHz CPU
+CONFIG_ESP32_DEFAULT_CPU_FREQ_80=
+CONFIG_ESP32_DEFAULT_CPU_FREQ_160=
+CONFIG_ESP32_DEFAULT_CPU_FREQ_240=y
+CONFIG_ESP32_DEFAULT_CPU_FREQ_MHZ=240

ports/esp32/boards/sdkconfig.base

@@ -11,7 +11,6 @@ CONFIG_APP_EXCLUDE_PROJECT_NAME_VAR=y
 CONFIG_BOOTLOADER_LOG_LEVEL_WARN=y
 
 # ESP32-specific
-CONFIG_ESP32_DEFAULT_CPU_FREQ_240=y
 CONFIG_ESP_TASK_WDT_CHECK_IDLE_TASK_CPU0=n
 CONFIG_ESP_TASK_WDT_CHECK_IDLE_TASK_CPU1=n
 CONFIG_ESP32_XTAL_FREQ_AUTO=y