Re-write gen_txb_cache
Re-write gen_txb_cache

This speed up lv_map exp by 5%

Change-Id: Ic71e55c9e777031fe671589a96d8f2053f4d65a5

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