[media] coda: add support for firmware files named as distributed by NXP

Try loading the firmware from firmware files named vpu_fw_imx*.bin, as
they are originally distributed by NXP. Fall back to v4l-coda*-imx6*.bin.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>