media: videodev2.h.rst.exceptions: add missing exceptions

Add new exceptions for V4L2_COLORSPACE_LAST, V4L2_XFER_FUNC_LAST
and V4L2_YCBCR_ENC_LAST.

This fixes documentation warnings:

Documentation/output/videodev2.h.rst:6: WARNING: undefined label: v4l2-colorspace-last
Documentation/output/videodev2.h.rst:6: WARNING: undefined label: v4l2-xfer-func-last
Documentation/output/videodev2.h.rst:6: WARNING: undefined label: v4l2-ycbcr-enc-last

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>