drivers: power: reset: Do cold reset when doing oem reboot

As the IMEM approach to store reset reason is deprecated, so use
the spare register in PMIC power-on peripheral to store the oem
restart reason.

Bit-2 to bit-7 of SOFT_RB_SPARE for hard reset reason, so divide
existing range into regions, value 0 to 31 for common defined features
and 32 to 63 values are for OEMs/ODMs specific features.

Change-Id: Ib8e64d6dd5a335325d0469280e41e9d10ec9b893
Signed-off-by: Lijuan Gao <lijuang@codeaurora.org>