There's no need to check for an incorrect number of data lanes in
imx290_set_data_lanes() as the value is validated at probe() time. Drop
the check.

The PHY_LANE_NUM and CSI_LANE_MODE registers are programmed with a value
equal to the number of lanes minus one. Compute it instead of handling
it in the switch/case.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>