[COMMON] media: smfc: invalid the cache lines as little as possible

[COMMON] media: smfc: invalid the cache lines as little as possible

The amount of data to invalidate CPU cache lines of the destination
buffer of the JPEG compression is much smaller than the length of
the destination buffer because the userspace tends to qbuf the buffer
that is large enough to store the uncompressed image.
Therefore, the data amount of invaidation on the destination buffer
needs to be less than the buffer size for less delay in cache
invalidation and vb2_ion_buf_finish_exact() is for that purpose.

Change-Id: Ifc069a3e940f4e470a2947dc249704340cbe5abb
Signed-off-by: Cho KyongHo <pullip.cho@samsung.com>