Update kernel headers to v3.18.3.

Bug: 19127803
Change-Id: I67fa0832322ddd0032d909476047578be052bcf2
diff --git a/libc/kernel/uapi/linux/xattr.h b/libc/kernel/uapi/linux/xattr.h
index 650cf93..a3bba74 100644
--- a/libc/kernel/uapi/linux/xattr.h
+++ b/libc/kernel/uapi/linux/xattr.h
@@ -19,7 +19,7 @@
 #include <linux/libc-compat.h>
 #ifndef _UAPI_LINUX_XATTR_H
 #define _UAPI_LINUX_XATTR_H
-#ifdef __UAPI_DEF_XATTR
+#if __UAPI_DEF_XATTR
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define __USE_KERNEL_XATTR_DEFS
 #define XATTR_CREATE 0x1