[media] v4l: Add camera pan/tilt speed controls

The V4L2_CID_PAN_SPEED and V4L2_CID_TILT_SPEED controls allow to move the
camera by setting its rotation speed around its axis.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>