v4l2-compliance: check for invalid m2m + overlay caps

The m2m + overlay capabilities combination makes no sense. Check for that.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
v4l2-compliance: check that streaming will fail for overlays

Overlay buftypes do not support streaming. Check for this.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>