Rework the locking in m2m driver to assure proper operation on SMP systems.

When job_abort or stop_streaming was called to immediately shutdown
a memory-to-memory transaction video buffers scheduled for processing
were never returned to vb2 and v4l2_m2m_job_finish was not called
which led to hanging.

Correct this and also return the unprocessed buffers to vb2 marking
them as erroneous, in case the end of frame interrupt do not occur.
Reported-by: Sewoon Park <seuni.park@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>