[media] s5p-mfc: Use decode status instead of display status on MFCv5

Commit 90c0ae50 changed how the frame_type of a decoded frame
gets determined, by switching from the get_dec_frame_type to
get_disp_frame_type operation. Unfortunately it seems that on MFC v5 the
result of get_disp_frame_type is always 0 (no display) when decoding
(tested with H264), resulting in no frame ever being output from the
decoder.

This patch reverts MFC v5 to the previous behaviour while keeping the
new behaviour for v6 and up.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>