Fix CONFIG_DAALA_DCT4/8/16 builds with CMake.
Fix CONFIG_DAALA_DCT4/8/16 builds with CMake.

Build aom_ports/x86/emms.asm for all x86 targets. It was
previously guarded by HAVE_MMX, which violates assumptions
established by the configure build.

BUG=aomedia:683

Change-Id: Icac2b0ba6272c61dbb71dfc3824a8cf391c251b6

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