[media] v4l: Add 16-bit raw bayer pixel formats

The formats added by this patch are:

	V4L2_PIX_FMT_SBGGR16
	V4L2_PIX_FMT_SGBRG16
	V4L2_PIX_FMT_SGRBG16

V4L2_PIX_FMT_SRGGB16 already existed before the patch. Rework the
documentation to match that of the other sample depths.

Also align the description of V4L2_PIX_FMT_SRGGB16 to match with other
similar formats.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>