[x64] add missing disassm of pcmpeqd

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/658063003

Patch from Weiliang Lin <weiliang.lin@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24680 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/disasm-x64.cc

@@ -1088,6 +1088,8 @@ int DisassemblerX64::TwoByteOpcodeInstruction(byte* data) {
           mnemonic = "ucomisd";
         } else if (opcode == 0x2F) {
           mnemonic = "comisd";
+        } else if (opcode == 0x76) {
+          mnemonic = "pcmpeqd";
         } else {
           UnimplementedInstruction();
         }