Btrfs: fix RHEL test for ClearPageFsMisc

Newer RHEL5 kernels define both ClearPageFSMisc and
ClearPageChecked, so test for both before redefining.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -1648,7 +1648,7 @@ int btrfs_csum_truncate(struct btrfs_trans_handle *trans,
 /* inode.c */
 
 /* RHEL and EL kernels have a patch that renames PG_checked to FsMisc */
-#ifdef ClearPageFsMisc
+#if defined(ClearPageFsMisc) && !defined(ClearPageChecked)
 #define ClearPageChecked ClearPageFsMisc
 #define SetPageChecked SetPageFsMisc
 #define PageChecked PageFsMisc