[runtime] Fix broken Mips big-endian build.

It was too early to remove SharedFunctionInfo::kCompilerHintsSize.

TBR=jkummerow@chromium.org

Bug: v8:6470
Change-Id: I6d4ff1399155ebb587896cc2b1f117df14bea082
Reviewed-on: https://chromium-review.googlesource.com/529130
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45827}

src/objects/shared-function-info.h

@@ -564,6 +564,8 @@ class SharedFunctionInfo : public HeapObject {
 
   inline int length() const;
 
+  static const int kCompilerHintsSize = kIntSize;
+
  public:
   // Constants for optimizing codegen for strict mode function and
   // native tests when using integer-width instructions.