power: smb1360: Move wake source handling to empty_soc handler

Empty SOC indicates that SOC is 0, hold a wake source
to allow userspace to take the necessary action.

While at it, update the logging information from the driver.

Change-Id: I6371e584eaf1bd51e81fe04e3584084cb8175903
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>