Improve high bitdepth CLPF SIMD

The high bitdepth was a direct translation of the low bit code, but
the tricks to keep 9 bit differences saturated within 8 bit are
redundant in high bitdepth, so the these were replaced with simpler
and more readable code.

Change-Id: I0710a1f1b9dcde8039d3dfa0f74cd2ea2b3bae27
1 file changed