[media] media v4l2-mem2mem: fix src/out and dst/cap num_rdy

src bufs belong to out queue, dst bufs belong to in queue. Currently
this is not a real problem since all users currently need exactly one
input and one output buffer.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>