In initMMX2HScaler, when chrDstW is not divisible by 4, the last filterPos...

In initMMX2HScaler, when chrDstW is not divisible by 4, the last filterPos element is initialized on the wrong index (not evenly aligned). This fixes it

Originally committed as revision 28933 to svn://svn.mplayerhq.hu/mplayer/trunk/libswscale