[COMMON] media: smfc: clean the dirty region by CPU in .buf_cleaup

[COMMON] media: smfc: clean the dirty region by CPU in .buf_cleaup

Even though userspace gives V4L2_BUF_FLAG_NO_CACHE_CLEAN flag in
the v4l2_buffer on qbuf, it just guarantees that the buffer after
the specific offset is not cache dirty by CPU.
If the offset become smaller than the previous, H/W may starts to
write the compressed stream on the area that may have dirty cache
lines.
To prevent the problem, the driver should clean the dirty cache lines
if the offset becomes no longer valied.

Change-Id: I54baba493dd4c179eda740bedba3378d4abe8435
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>