usb: gadget: uvc: Make color matching attributes read/write

In preparation for allowing more than the default color matching
descriptor, make the color matching attributes writeable.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Link: https://lore.kernel.org/r/20230202114142.300858-6-dan.scally@ideasonboard.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>