sdkconfig.base: Add CONFIG_BOOTLOADER_SKIP_VALIDATE_IN_DEEP_SLEEP=y.
This reduces time to boot from deepsleep by at least 200ms and can
provide significant power savings for deepsleep-based battery
applications.
docs/library/esp32.rst: Add note cautioning not to enter deepsleep after
changing the boot partition, without first performing a hard reset.
Signed-off-by: Glenn Moloney <glenn.moloney@gmail.com>