media: v4l2-mem2mem: Simplify exiting the function in __v4l2_m2m_try_schedule

The __v4l2_m2m_try_schedule function acquires and releases multiple
spinlocks. Simplify unlocking the job lock by adding labels to unlock
the lock and exit the function.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>