Use 10 bits to represent adapt_scan probabilities
Use 10 bits to represent adapt_scan probabilities

The performance drop slightly by using 10 bit probabilities.
lowres: -0.048%
midres: 0.007
hdres: -0.06

Change-Id: I5ba7b5607802d084a599b779e5745f88b31e2cbe

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