[media] s5p-fimc: Set default image format at device open()

Make sure a valid image format is initially set on both the CAPTURE
and the OUTPUT buffer queue.

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>