Consistently say va_arg rather than __va_arg.

Bug: http://b/64250392
Test: builds
Change-Id: I435242f620245d825b8a68365c71c99a60aba625
diff --git a/libc/include/bits/fortify/stdio.h b/libc/include/bits/fortify/stdio.h
index 22dc217..a36ac32 100644
--- a/libc/include/bits/fortify/stdio.h
+++ b/libc/include/bits/fortify/stdio.h
@@ -39,13 +39,13 @@
 #if __ANDROID_API__ >= __ANDROID_API_J_MR1__
 __BIONIC_FORTIFY_INLINE __printflike(3, 0)
 int vsnprintf(char *const __pass_object_size dest, size_t size,
-              const char *_Nonnull format, __va_list ap) __overloadable {
+              const char *_Nonnull format, va_list ap) __overloadable {
     return __builtin___vsnprintf_chk(dest, size, 0, __bos(dest), format, ap);
 }
 
 __BIONIC_FORTIFY_INLINE __printflike(2, 0)
 int vsprintf(char *const __pass_object_size dest, const char *_Nonnull format,
-             __va_list ap) __overloadable {
+             va_list ap) __overloadable {
     return __builtin___vsprintf_chk(dest, 0, __bos(dest), format, ap);
 }
 #endif /* __ANDROID_API__ >= __ANDROID_API_J_MR1__ */