[media] coda: store IRAM size in struct coda_devtype

Similarly to workbuf_size and tempbuf_size, store iram_size in the
coda_devtype structure. This also decreases the IRAM used on i.MX6DL
to 128 KiB.

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>