msm: vidc: Reset stop_called state when START is called

The driver needs to reset the stop_called field once START called.
Otherwise in START, STOP, START, STOP sequences the secondary STOP
will be treated as a duplicate STOP and ignored.

Change-Id: I7104ba6c4dbeda06704c46d836f9b7623fa36146
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>