commit ebe864a6 upstream.

The conversion to videobuf2 failed to check the return value of
vb2_qbuf(). Fix it.
Reported-by: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-By: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>