[media] DocBook media: fix VIDIOC_CROPCAP type description

The type field of VIDIOC_CROPCAP does not allow the MPLANE variants, just
as all the other crop/selection related ioctls.

Fix the description of CROPCAP and G_CROP and make the text describing
this consistent for all selection ioctls.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>