Btrfs: fix btrfs acl #ifdef checks

The btrfs acl code was #ifdefing for a define
that didn't exist.  This correctly matches it
to the values used by the Kconfig file.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/xattr.c

@@ -260,7 +260,7 @@ err:
  * attributes are handled directly.
  */
 struct xattr_handler *btrfs_xattr_handlers[] = {
-#ifdef CONFIG_BTRFS_POSIX_ACL
+#ifdef CONFIG_BTRFS_FS_POSIX_ACL
 	&btrfs_xattr_acl_access_handler,
 	&btrfs_xattr_acl_default_handler,
 #endif