FROMLIST: power: reset: add reboot mode driver

FROMLIST: power: reset: add reboot mode driver

This driver parse the reboot commands like "reboot loader"
and "reboot recovery" to get a boot mode described in the
device tree , then call the write interfae to store the boot
mode in some place like special register or sram , which can
be read by the bootloader after system reboot, then the bootloader
can take different action according to the mode stored.

This is commonly used on Android based devices, in order to
reboot the device into fastboot or recovery mode.

Change-Id: Ifce5a22493a52f3e15332bbf3c94ce7217d7d17c
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: John Stultz <john.stultz@linaro.org>