Constify subtarget info properly so that we dont cast away the const in
the SubtargetInfoKV tables. Found by gcc48 -Wcast-qual.

llvm-svn: 163251
diff --git a/llvm/lib/MC/SubtargetFeature.cpp b/llvm/lib/MC/SubtargetFeature.cpp
index 0a44e77..f43197b 100644
--- a/llvm/lib/MC/SubtargetFeature.cpp
+++ b/llvm/lib/MC/SubtargetFeature.cpp
@@ -337,9 +337,9 @@
 }
 
 /// Get scheduling itinerary of a CPU.
-void *SubtargetFeatures::getItinerary(const StringRef CPU,
-                                      const SubtargetInfoKV *Table,
-                                      size_t TableSize) {
+const void *SubtargetFeatures::getItinerary(const StringRef CPU,
+                                            const SubtargetInfoKV *Table,
+                                            size_t TableSize) {
   assert(Table && "missing table");
 #ifndef NDEBUG
   for (size_t i = 1; i < TableSize; i++) {