msm: smd_pkt: Handle wakelocks appropriately to optimize power usage

If the user-space application performs a poll() operation before a
read() operation, then release the wakelock in the read operation.
This is under the assumption that user-space application can grab a
wakelock between poll() and read() operations. If the user-space
application does not perform poll() operation at all before read()
operation, then allow the wakelock to timeout and release itself.

CRs-Fixed: 337654
Change-Id: I179248512b26841ed7f15318645d56cceec9b458
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>