[media] coda: simplify frame memory control register handling

Since the firmware newer writes to FRAME_MEM_CTRL, we can initialize it once
per context (incidentally, we already do write it in coda_hw_init) and never
have to read it back.

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