Update av1_read_coeffs_txb(), keep update position
Update av1_read_coeffs_txb(), keep update position

Change-Id: I3acd24acbd121c93e89817f865a54327d5e8e92e

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