btrfs: use ioctl args support mask for device delete

When the device remove v2 ioctl was added, the full support mask was
added to sanity check the flags. However this would allow to let the
subvolume related flags to be accepted. This is not supposed to happen.

Use the correct support mask, which means that now any of
BTRFS_SUBVOL_CREATE_ASYNC, BTRFS_SUBVOL_RDONLY or
BTRFS_SUBVOL_QGROUP_INHERIT will be rejected as ENOTSUPP. Though this is
a user-visible change, specifying subvolume flags for device deletion
does not make sense and there are hopefully no applications doing that.
Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3075,8 +3075,7 @@ static long btrfs_ioctl_rm_dev_v2(struct file *file, void __user *arg)
 		goto err_drop;
 	}
 
-	/* Check for compatibility reject unknown flags */
-	if (vol_args->flags & ~BTRFS_VOL_ARG_V2_FLAGS_SUPPORTED) {
+	if (vol_args->flags & ~BTRFS_DEVICE_REMOVE_ARGS_MASK) {
 		ret = -EOPNOTSUPP;
 		goto out;
 	}