[media] v4l: vsp1: Fix V4L2_PIX_FMT_XRGB444 format definition

The format is erroneously defined with an alpha channel. Fix it.

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