v4l2_m2m_job_finish(), which is called from the interrupt handler with
slock acquired, can call the device_run() hook immediately if another
context was in the queue. This hook also acquires slock, resulting in
a deadlock for this scenario.
Fix this by releasing slock right before calling v4l2_m2m_job_finish().
This is safe to do as the state of the hardware cannot change before
v4l2_m2m_job_finish() is called anyway.