media: uapi: v4l: Change V4L2_TYPE_IS_CAPTURE condition

Explicitly compare a buffer type only with valid buffer types,
to avoid matching a buffer type outside of the valid buffer type set.

Signed-off-by: Nas Chung <nas.chung@chipsnmedia.com>
Reviewed-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>