Correct the golomb cost in av1_cost_coeffs_txb()
Correct the golomb cost in av1_cost_coeffs_txb()

bug=aomedia:1516

Change-Id: I48b9fe3c971d82e03c4b6e9014beafa59110baea

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