[media] s5p_mfc: correct the loop condition

It should take ctx->dst_fmt->num_planes as
the loop condition for CAPTURE.

Signed-off-by: Zhaowei Yuan <zhaowei.yuan@samsung.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>