BACKPORT: PM: wakeup_reason: add functions to query and clear wakeup reasons

The query results are valid until the next PM_SUSPEND_PREPARE.

(cherry picked from commit 76543de14f860ab713114621cb62e8006b7ca952)
Change-Id: I6bc2bd47c830262319576a001d39ac9a994916cf
Signed-off-by: Iliyan Malchev <malchev@google.com>
Git-commit: a32e34cb36d558ceb0e9d5658568f062a6284c7c
Git-repo: https://android.googlesource.com/kernel/msm


Signed-off-by: Venkatesh Yadav Abbarapu <vabbar@codeaurora.org>