media: uvcvideo: Use clamp() to replace manual implementation

The kernel has a nice clamp() macro, use it to replace a manual
implementation based on min() and max(). No functional change is
intended.

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