Fix typo for DIST_8X8 in cmake defaults.
Fix typo for DIST_8X8 in cmake defaults.

Change-Id: I8987dbc05dc79d33eeadebb427095fafa319e9fd

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