Remove CheckNotRegistersEqual regexp-masm function from all architectures.

src/x64/regexp-macro-assembler-x64.cc

Index: src/x64/regexp-macro-assembler-x64.cc
diff --git a/src/x64/regexp-macro-assembler-x64.cc b/src/x64/regexp-macro-assembler-x64.cc
index bf232bff9b523413a674ff3adc443177262a20d4..088d3135a6987538a6a93143a4068e7f9d446dbc 100644
--- a/src/x64/regexp-macro-assembler-x64.cc
+++ b/src/x64/regexp-macro-assembler-x64.cc
@@ -523,15 +523,6 @@ void RegExpMacroAssemblerX64::CheckNotBackReference(
 }
 
 
-void RegExpMacroAssemblerX64::CheckNotRegistersEqual(int reg1,
-                                                     int reg2,
-                                                     Label* on_not_equal) {
-  __ movq(rax, register_location(reg1));
-  __ cmpq(rax, register_location(reg2));
-  BranchOrBacktrack(not_equal, on_not_equal);
-}
-
-
 void RegExpMacroAssemblerX64::CheckNotCharacter(uint32_t c,
                                                 Label* on_not_equal) {
   __ cmpl(current_character(), Immediate(c));