[media] em28xx: remove ioctl VIDIOC_CROPCAP

The em28xx driver doesn't support the VIDIOC_G_CROP and VIDIOC_S_CROP ioctls,
so VIDIOC_CROPCAP is useless and has the potential to confuse applications,
because it can be interpreted as indicator for cropping support.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>