AOM_QM: constrain high-weight matrices to stay in 8 bits.
AOM_QM: constrain high-weight matrices to stay in 8 bits.

Modify the HF weights for high-weight (qmindex<5) matrices
to avoid stray values > 255. These matrices do not affect
the normal QM settings when QM is enabled.

Change-Id: I0bfb59279570f3336d49273b374202bda3ce921c

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom