[media] coda: add sequence counter offset

The coda h.264 decoder also counts PIC_RUNs where no frame was decoded but
a frame was rotated out / marked as ready to be displayed. This causes an
offset between the incoming encoded frame's sequence number and the decode
sequence number returned by the coda. This patch introduces a sequence
counter offset variable to keep track of the difference.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>