[media] media: coda: firmware loading for 64-bit AXI bus width

Add support for loading a raw firmware with 16-bit chars ordered in
little-endian 64-bit words, corresponding to the memory access pattern
of CODA7 and above: When writing the boot code into the code download
register, the chars have to be reordered back.

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>