Work around a swizzle/mask bug

Apparently "mul ft3.yzw, ft3.yzw, ft2.yyy" doesn't do what it looks like
it should do, though "mul ft3.xyz, ft3.xyz, ft2.yyy" works fine. In
order to use the latter as a workaround I've rearranged the allocation
of ft3's components in the code surrounding the multiplication in
question.