Fix typo in PrintfConversionSpecifier::isDoubleArg()

This makes the printf diagnostics issue warnigns for %a, %A, %e, etc.
when used with the wrong argument.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150370 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/format-strings.c b/test/Sema/format-strings.c
index dcff75a..a7b40f8 100644
--- a/test/Sema/format-strings.c
+++ b/test/Sema/format-strings.c
@@ -471,6 +471,8 @@
 
   const char kFormat17[] = "%hu"; // expected-note{{format string is defined here}}}
   printf(kFormat17, (int[]){0}); // expected-warning{{format specifies type 'unsigned short' but the argument}}
+
+  printf("%a", (long double)0); // expected-warning{{format specifies type 'double' but the argument has type 'long double'}}
 }
 
 // PR 9466: clang: doesn't know about %Lu, %Ld, and %Lx