Add "CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE=y" to
ports/esp32/boards/sdkconfig.base so that all micropython esp32 images
support OTA rollback in the bootloader. These images can then be converted
to OTA-capable images as required by user tools.
Also remove CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE=y from board-specific
sdkconfig files as this is now the default.
Signed-off-by: Glenn Moloney <glenn.moloney@gmail.com>
