[media] s5p-tv: Report only multi-plane capabilities in vidioc_querycap

The mixer video node supports only multi-planar API so the driver
should not be setting V4L2_CAP_VIDEO_OUTPUT flags. Fix this and
also switch to device_caps. Additionally fix the VIDIOC_ENUM_FMT
ioctl handler which now works for V4L2_BUF_TYPE_CAPTURE, rather
than expected V4L2_BUF_TYPE_CAPTURE_MPLANE.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>