media: imx: add 16-bit grayscale support

Since commit 50b0f0ae

 ("gpu: ipu-csi: add 10/12-bit grayscale
support to mbus_code_to_bus_cfg") the IPU CSI can be configured to
capture 10-bit and 12-bit grayscale formats, expanded to 16-bit
grayscale, in bayer/generic data mode.
This patch adds support for V4L2_PIX_FMT_Y16 captured from sensors
that provide MEDIA_BUS_FMT_Y10_1X10 or MEDIA_BUS_FMT_Y12_1X12 data.

Cc: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>