Correct ssse3 8/16-pixel wide sub-pixel filter calculation

Although no mismatch was indicated for 8/16 wide sub-pixel filters
in issue 661, they had similar problems that could cause mismatch
potentially. This patch fixed calculations in HORIZx8/16
and VERTx8/16.

Change-Id: Ib85412d690bea5609a51f0e50e7c858406b8ff9e
1 file changed