[msm8660] Add support for reboot reason code

Linux kernel writes to shared location in APPSBL EBI; apps bootloader
reads this location the reboot reason, scrubs it and acts accordingly.

This location may move to IMEM area in future once room is made for
HLOS in IMEM.

Change-Id: I39b45cad6bbd25fdbc513ef74eb2608fc8b37cf8
2 files changed