[media] coda: simplify IRAM setup

OVL and BTP IRAM buffers are never used, setup the bits for
for DBK/BIT/IP usage depending on CODA version in one place.
Also, use a simple allocator function and group IRAM addresses
and size in a coda_aux_buf structure.
This is done in preparation for CODA960 support.

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>