V4L/DVB: uvcvideo: Power line frequency control doesn't support GET_MIN/MAX/RES

Issuing a GET_MIN request on the power line frequency control times out
on at least the Apple iSight. As the UVC specification doesn't list
GET_MIN/MAX/RES as supported on that control, remove them from the
uvc_ctrls array.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>