[media] omap_vout: fix compiler warning

media-git/drivers/media/platform/omap/omap_vout.c: In function ‘omapvid_init’:
media-git/drivers/media/platform/omap/omap_vout.c:382:17: warning: ‘mode’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  vout->dss_mode = video_mode_to_dss_mode(vout);
                 ^
media-git/drivers/media/platform/omap/omap_vout.c:332:23: note: ‘mode’ was declared here
  enum omap_color_mode mode;
                       ^

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Prabhakar Lad <prabhakar.lad@ti.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>