[media] media: coda: fix IRAM/AXI handling for i.MX53

This uses the ARCH_MXC specific iram_alloc API to allocate a work
buffer in the SoC's on-chip SRAM and sets up the AXI_SRAM_USE
register. In the future, the allocation will be converted to use
the genalloc API.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>