media: rp1: cfe: Add a csi_dt value for 16bit formats

Raw 16bit formats didn't have a csi_dt value defined, which
presumably would trip the WARN_ON(!fmt->csi_dt); in
cfe_start_channel.

The value is defined in CSI2 v2.0 as 0x2e, so set it accordingly.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>