vp10/rdopt: quiet unused variable warning
vp10/rdopt: quiet unused variable warning

when CONFIG_REF_MV and CONFIG_EXT_INTER are enabled

Change-Id: I17fa2b5fe0e1878333099cc5fa2b1ee36636b4d3

smarter/aom,mbebenita/aom,mbebenita/aom,smarter/aom,mbebenita/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,luctrudeau/aom,mbebenita/aom,luctrudeau/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,smarter/aom,luctrudeau/aom,mbebenita/aom