ANS: Remove extra buffer size checks causing a false decode error.
ANS: Remove extra buffer size checks causing a false decode error.

The minimal ans partition size is now one byte. This is checked in
ans_read_init().

The read_is_valid() condition is handled by setup_token_decoder().

Change-Id: I7b202b896630bc4285532208bf7cf84567afe158

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