CHROMIUM: rk3288-vpu: Add DMABUF to io_modes.

CHROMIUM: rk3288-vpu: Add DMABUF to io_modes.

To support gralloc buffers.

BUG=chrome-os-partner:45346
TEST=Play a video on minnie.

Signed-off-by: Owen Lin <owenlin@google.com>
Reviewed-on: https://chromium-review.googlesource.com/299613
Commit-Ready: Owen Lin <owenlin@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Change-Id: I7ba9c7a0640fa822c43f2442ddbdc257609bc09a
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>