btrfs: rename btrfs_close_extra_device to btrfs_free_extra_devids

This function btrfs_close_extra_devices() is about freeing
extra devids which once it may have belonged to this filesystem.
So rename it and add the comment. The _devid suffix is
appropriate as this function won't handle devices which are
outside of the filesytem being mounted.

Signed-off-by: Anand Jain <[email protected]>
Signed-off-by: David Sterba <[email protected]>
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index d28f574..d1fcaea 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -422,7 +422,7 @@ 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_devices *fs_devices, int step);
+void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step);
 void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
 		struct btrfs_device *device, struct btrfs_device *this_dev);
 int btrfs_find_device_missing_or_by_path(struct btrfs_fs_info *fs_info,