Remove compound mode newmv check
Remove compound mode newmv check

discount_newmv_test is only triggered in NEWMV mode, so we don't
need to check the NEW_NEWMV mode here

STATS_CHANGED about 0.005%

Change-Id: I8a0573dd7083d097f722aa2c89ada540a9565955

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