power_mgmt: Simplify _sys_soc_resume notification

_sys_soc_resume hook is over loaded to handle to different
scenarios. It is primarily called to notify exit of kernel idling
after PM operations. It is also used to notify exit from deep sleep.
This is very confusing and also makes the implementation of the
hook function very difficult because of very different conditions
involved in the 2 different use cases. Further, users may not require
either or both use cases depending of their custom boot flow and
power state handling. To simplify, create a separate hook for the
purpose of deep sleep exit notification. Use the existing one to
only notify kernel idling exit after PM operations.

Jira: ZEP-1256
Change-Id: I96350199a0fd37f16590c8ee5302a94a3d71b8ba
Signed-off-by: Ramesh Thomas <ramesh.thomas@intel.com>