media: uvcvideo: Make uvc_control_mapping menu_info field const

The menu_info field of the uvc_control_mapping structure points to an
array of menu info data that are never changed by the driver. Make the
pointer const and constify the related static arrays in the driver.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>