Split X86::BI__builtin_cpu_init handling into own function[NFC]

The Cpu Init functionality is required for the target
attribute, so this patch simply splits it out into its own
function, exactly like CpuIs and CpuSupports.

llvm-svn: 315075
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 68be87f..3ec3466 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3901,6 +3901,7 @@
   llvm::Value *EmitX86CpuIs(StringRef CPUStr);
   llvm::Value *EmitX86CpuSupports(const CallExpr *E);
   llvm::Value *EmitX86CpuSupports(ArrayRef<StringRef> FeatureStrs);
+  llvm::Value *EmitX86CpuInit();
 };
 
 /// Helper class with most of the code for saving a value for a