ENGR00161948 mxc v4l2 output: fix case of input crop with xoffset

ENGR00161948 mxc v4l2 output: fix case of input crop with xoffset

run test like:
/unit_tests//mxc_v4l2_output.out -iw 1280 -ih 720 -cr 1024 700 40 0 -ow 1024
-oh 700 /unit_tests/720p.yuv
Under IPU IC bypass mode, the output color is not correct.
And sometimes come out tearing issue.

Fix them by modify fb driver adding xpanstep support and set vb->state to DONE
after it finish show.

When previous videobuf finish show and next videobuf ready to show, set
VIDEOBUF_DONE state to avoid tearing issue, which make sure showing buffer will
not be dequeue to write new data. It also bring side-effect that the last buffer
can not be dequeue correctly, app need take care about it.

Signed-off-by: Jason Chen <b02280@freescale.com>