Speedup find_tx_size_rd_info
Speedup find_tx_size_rd_info

1. Replace mod in the loop by spliting to two loops

2. For encoder, about 0.6% faster shows by encoding
20 frame of BasketballDrill_832x480_50.y4m.
( 397483 ms -> 394976 ms)

Change-Id: Idfe41c184729c453a910c794e7ddbf24717070ff

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