Support rectangular tx_size distortion calculation by default
Support rectangular tx_size distortion calculation by default

Remove the CONFIG_EXT_TX flag.

Change-Id: I7e35036156e116a2c00c982a8d57473258e002ea

GrokImageCompression/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,mbebenita/aom,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,mbebenita/aom,mbebenita/aom,smarter/aom,GrokImageCompression/aom,luctrudeau/aom,mbebenita/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,smarter/aom