power: vm_bms: Release the wake-source after an OCV update

The VBMS driver holds a wake-source for the userspace to pick
up the data for processing, this wake-source stays held for
500ms (timeout) which may stall a system suspend if the data
processing is complete.
Fix this by releasing the wake-source after the userspace has
written back OCV which indicates that processing is complete.

Change-Id: Id527881800407f5b7476b62dd86f805c00304689
Signed-off-by: Shilpa Suresh <sbsure@codeaurora.org>