gpu: ipu-v3: csi: support RGB565 on parallel bus

The CSI_SENS_CONF_DATA_FMT_RGB565 configuration only works for MIPI
CSI-2 sources. On the parallel bus, we need to use bayer (generic) mode
instead. To handle this difference, we pass the mbus_type to
mbus_code_to_bus_cfg().

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
[p.zabel@pengutronix.de - renamed rc to ret for consistency]
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>