btrfs: remove fs/btrfs/compat.h

fs/btrfs/compat.h only contained trivial macro wrappers of drop_nlink()
and inc_nlink().  This doesn't belong in mainline.

Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/ioctl.c

@@ -44,7 +44,6 @@
 #include <linux/uuid.h>
 #include <linux/btrfs.h>
 #include <linux/uaccess.h>
-#include "compat.h"
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"