Combine duplicate tx_class define in av1_read_coeffs_txb
Combine duplicate tx_class define in av1_read_coeffs_txb

Change-Id: I67992c18737eb9eef3759b2e3a13cf43df444760

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