staging: vc04_services: codec: Add support for V4L2_PIX_FMT_RGBA32 format

We already support V4L2_PIX_FMT_BGR32 which is the same thing with red
and blue swapped, so it makes sense to include this variant as well.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>