media: adv748x-csi2: Implement enum_mbus_codes

Define a list of supported mbus codes for the TXA and TXB CSI-2
transmitters and implement the enum_mbus_code operation.

The TXB transmitter only support YUV422 while the TXA one supports
multiple formats as reported by the chip's manual in section 9.7.
but the HDMI and AFE subdevices only provide RGB888 and YUV422, so only
list those ones here.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20240617161135.130719-6-jacopo.mondi@ideasonboard.com


Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>