msm: VPU: Fix handling of config changes after first commit

After initial session configuration is applied, further config changes
can get lost if they are made before session streaming is started.
Fix by resetting commit_state flag so that new config changes are sent
to firmware on next Streamon/Commit ioctls.

Change-Id: I0cc5682e7362fcf9e918e908fb7bd0dbc1b2bd6d
Signed-off-by: Stephane Viau <sviau@codeaurora.org>