drm/omap: remove VFL_TYPE_GRABBER

The commit dc42cf74
(media: v4l2-dev.h: remove VFL_TYPE_GRABBER) has removed the VFL_TYPE_GRABBER.
So replace the VFL_TYPE_GRABBER with VFL_TYPE_VIDEO.

Signed-off-by: Xulin Sun <xulin.sun@windriver.com>