SAP: Dynamic use of wake locks

This changes the way wake locks are used for SAP from acquiring
wake lock at connect, and releasint at disconnect to acquiting
a wake lock each time activity is detected, either between
Bluetooth and the RIL or between Bluetooth and the client.
The wake lock is released when there has been no activity for
one second.

This is the same scheme as for MAP, except using a lower timeout
value, based on analysis of the traffic when connected to a
Nokia 616 car-kit.

Change-Id: Ie4bcf7e991d81e88b64dc4ba20fa74b327fde3c6
Signed-off-by: Casper Bonde <c.bonde@samsung.com>