The v_overlap_filter needs to run on the colocated block of the previous
macroblock. For the luma plane, the colocated block is located two blocks
on the left instead of one. In addition, the overlap filter needs to run
on the non-edge blocks of the first macroblock row and column.

Fixes ticket #7171.
Signed-off-by: Jerome Borsboom <jerome.borsboom@carpalis.nl>