[FFmpeg-soc] Another loop filter

[Kostya]

Looks like RV30 uses another loop filter which looks like
simplified version of rv34_weak_filter:

 t = ((src[-1] - src[0]) - (src[-2] - src[1])<<2) >> 3;
 t = clip(t, -A, A);
 src[-1] = clip_uint8(src[-1] + t);
 src[ 0] = clip_uint8(src[ 0] - t);

loop filter operates on 8x8 blocks,
pixels 0-3 use one parameter, 4-7 use another one

Is that known version as well?