media: uvcvideo: Fix power line control for a Chicony camera

The device does not implement the control properly.

Fixes v4l2-compliance error:

info: checking control 'Power Line Frequency' (0x00980918)
fail: v4l2-test-controls.cpp(552): could not set valid menu item 3

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>