Fix ifdef macro missed in previous commit

llvm-svn: 191003
diff --git a/clang/lib/Headers/shaintrin.h b/clang/lib/Headers/shaintrin.h
index 207485d..66ed055 100644
--- a/clang/lib/Headers/shaintrin.h
+++ b/clang/lib/Headers/shaintrin.h
@@ -21,7 +21,7 @@
  *===-----------------------------------------------------------------------===
  */
 
-#ifndef __X86INTRIN_H
+#ifndef __IMMINTRIN_H
 #error "Never use <shaintrin.h> directly; include <immintrin.h> instead."
 #endif