idct.c: remove dead functions
idct.c: remove dead functions

Change-Id: Ib876d906e158437d9a87870e2f5fb950fce28979

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