[ic] Fix megamorphic stub cache probing on some platforms.

src/ic/ppc/stub-cache-ppc.cc

Index: src/ic/ppc/stub-cache-ppc.cc
diff --git a/src/ic/ppc/stub-cache-ppc.cc b/src/ic/ppc/stub-cache-ppc.cc
index ee178f0678713813a638b73303bf1c15e0b0948a..fdeb3fac5f5c3317297d6ac411075f409fa88539 100644
--- a/src/ic/ppc/stub-cache-ppc.cc
+++ b/src/ic/ppc/stub-cache-ppc.cc
@@ -17,7 +17,8 @@ namespace internal {
 static void ProbeTable(StubCache* stub_cache, MacroAssembler* masm,
                        Code::Flags flags, StubCache::Table table,
                        Register receiver, Register name,
-                       // Number of the cache entry, not scaled.
+                       // The offset is scaled by 4, based on
+                       // kCacheIndexShift, which is two bits
                        Register offset, Register scratch, Register scratch2,
                        Register offset_scratch) {
   ExternalReference key_offset(stub_cache->key_reference(table));