libstagefright: Set session id to one for LPA playback

-ALSA HAL needs to differentiate between LPA and Tunnel mode
 playback for setting the correct routing path.
-The session id for LPA playback is set to one.

CRs-Fixed: 352002
(cherry picked from commit 5382f7f8feb609dfecae961641b0b5b0b6218371)

Change-Id: Id8b88ad838ce307b907444d4c5b9e25c3c3a19f3