MIPS: Make the mips port build cleanly with clang.

src/mips/macro-assembler-mips.h

Index: src/mips/macro-assembler-mips.h
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index 4198f8ba165d45cdbf16f4afdb95a2e71523f113..125cc8aaf3872efb63479e69824416fc283249bb 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -1565,7 +1565,6 @@ class CodePatcher {
 
  private:
   byte* address_;  // The address of the code being patched.
-  int instructions_;  // Number of instructions of the expected patch size.
   int size_;  // Number of bytes of the expected patch size.
   MacroAssembler masm_;  // Macro assembler used to generate the code.
 };