CHROMIUM: s5p-mfc: Fix input/output format reporting

CHROMIUM: s5p-mfc: Fix input/output format reporting

The video encode/decode paths have duplicated logic between
VIDIOC_TRY_FMT and VIDIOC_S_FMT that should be de-duped.  Also, video
decode reports V4L2_PIX_FMT_NV12MT_16X16 output format, regardless of
what the actual output has been set at.  Fix this.

Signed-off-by: John Sheu <sheu@google.com>
BUG=chromium-os:38376
TEST=local build, run on snow

Change-Id: I3c4c5258733421f54340ca8237d2c5200cb76fc4
Reviewed-on: https://gerrit.chromium.org/gerrit/43676
Reviewed-by: Pawel Osciak <posciak@chromium.org>
Commit-Queue: John Sheu <sheu@chromium.org>
Tested-by: John Sheu <sheu@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/45654
Reviewed-by: John Sheu <sheu@chromium.org>