btrfs: Do not restrict writes to btrfs devices

btrfs: Do not restrict writes to btrfs devices

Btrfs device probing code needs adaptation so that it works when writes
are restricted to its mounted devices. Since btrfs maintainer wants to
merge these changes through btrfs tree and there are review bandwidth
issues with that, let's not block all other filesystems and just not
restrict writes to btrfs devices for now.

CC: <linux-btrfs@vger.kernel.org>
CC: David Sterba <dsterba@suse.com>
CC: Josef Bacik <josef@toxicpanda.com>
CC: Chris Mason <clm@fb.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231101174325.10596-4-jack@suse.cz
Acked-by: David Sterba <dsterba@suse.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>