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>

fs/btrfs/volumes.h

@@ -421,8 +421,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
 			  struct btrfs_fs_devices **fs_devices_ret);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
-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);
 int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
 					 char *device_path,
 					 struct btrfs_device **device);