soc: nordic: add option for forcing RAM power on reboot

RAM power configuration is preserved through soft reset,
meaning that there is a risk of accessing powered off RAM blocks
when booting in different application (i.e. bootloader).
Add option to force all RAM blocks to be powered on
before triggering soft reset to prevent this from happening.

Signed-off-by: Nikodem Kastelik <nikodem.kastelik@nordicsemi.no>