The Simple Boot feature for Espressif chips is a method of booting
that doesn't depend on a 2nd stage bootloader. Its not the
intention to replace a 2nd stage bootloader such as MCUboot and
ESP-IDF bootloader, but to have a minimal and straight-forward way
of booting, and also simplify the building.
This commit also removes deprecated code and makes this bootloader
configuration as default for esp32s2 targets and removes the need
for running 'make bootloader' command for it.
Signed-off-by: Almir Okato <almir.okato@espressif.com>
