btrfs: remove unused fs_info arg from btrfs_close_extra_devices()

The commit:
8dabb74 Btrfs: change core code of btrfs to support the
        device replace operations
added the fs_info argument, but never used it -
just remove it again.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d7d1dde..6d4fb24 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -609,8 +609,7 @@
 	return ERR_PTR(-ENOMEM);
 }
 
-void btrfs_close_extra_devices(struct btrfs_fs_info *fs_info,
-			       struct btrfs_fs_devices *fs_devices, int step)
+void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices, int step)
 {
 	struct btrfs_device *device, *next;
 	struct btrfs_device *latest_dev = NULL;