highbd_quantize_intrin_sse2.c: add missing rtcd include
highbd_quantize_intrin_sse2.c: add missing rtcd include

quiets -Wmissing-prototypes warnings

BUG=b/29584271

Change-Id: Iff5214df0d1781810afbfc20bfaf664f109e2f29

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