Refactor search_txk_type
Refactor search_txk_type

1. Reduce the loops of uv_plane since tx_type should be the same as y_plane
2. Don't check ref_tx_type if allowed_tx_mask is already 0

Change-Id: I495d5db58fedcf72a888f75e70b8bd7530a5a194

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