[media] s5p-mfc: added support for end of stream handling in MFC encoder

[media] s5p-mfc: added support for end of stream handling in MFC encoder

s5p-mfc encoder after receiving V4L2_ENC_CMD_STOP command
will instruct MFC device to release all encoded frames.
After dequeuing last encoded frame driver will generate
V4L2_EVENT_EOS event.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>