btrfs: zoned: fix missing RCU locking in error message when loading zone info

At btrfs_load_zone_info() we have an error path that is dereferencing
the name of a device which is a RCU string but we are not holding a RCU
read lock, which is incorrect.

Fix this by using btrfs_err_in_rcu() instead of btrfs_err().

The problem is there since commit 08e11a3db098 ("btrfs: zoned: load zone's
allocation offset"), back then at btrfs_load_block_group_zone_info() but
then later on that code was factored out into the helper
btrfs_load_zone_info() by commit 09a46725cc84 ("btrfs: zoned: factor out
per-zone logic from btrfs_load_block_group_zone_info").

Fixes: 08e11a3db098 ("btrfs: zoned: load zone's allocation offset")
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Qu Wenruo <[e-mail]>
Reviewed-by: Naohiro Aota <[e-mail]>
Signed-off-by: Filipe Manana <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/zoned.c

···
 	switch (zone.cond) {
 	case BLK_ZONE_COND_OFFLINE:
 	case BLK_ZONE_COND_READONLY:
-		btrfs_err(fs_info,
+		btrfs_err_in_rcu(fs_info,
 		"zoned: offline/readonly zone %llu on device %s (devid %llu)",
 			  (info->physical >> device->zone_info->zone_size_shift),
 			  rcu_str_deref(device->name), device->devid);