sysfs: check visibility before changing group attribute ownership

In the Linux kernel, the following vulnerability has been resolved:

sysfs: check visibility before changing group attribute ownership

Since commit 0c17270f9b92 ("net: sysfs: Implement is_visible for
phys_(port_id, port_name, switch_id)"), __dev_change_net_namespace() can
hit WARN_ON() when trying to change owner of a file that isn't visible.
See the trace below:

WARNING: CPU: 6 PID: 2938 at net/core/dev.c:12410 __dev_change_net_namespace+0xb89/0xc30
CPU: 6 UID: 0 PID: 2938 Comm: incusd Not tainted 6.17.1-1-mainline #1 PREEMPT(full) 4b783b4a638669fb644857f484487d17cb45ed1f
Hardware name: Framework Laptop 13 (AMD Ryzen 7040Series)/FRANMDCP07, BIOS 03.07 02/19/2025
RIP: 0010:__dev_change_net_namespace+0xb89/0xc30
[...]
Call Trace:
<TASK>
? if6_seq_show+0x30/0x50
do_setlink.isra.0+0xc7/0x1270
? __nla_validate_parse+0x5c/0xcc0
? security_capable+0x94/0x1a0
rtnl_newlink+0x858/0xc20
? update_curr+0x8e/0x1c0
? update_entity_lag+0x71/0x80
? sched_balance_newidle+0x358/0x450
? psi_task_switch+0x113/0x2a0
? __pfx_rtnl_newlink+0x10/0x10
rtnetlink_rcv_msg+0x346/0x3e0
? sched_clock+0x10/0x30
? __pfx_rtnetlink_rcv_msg+0x10/0x10
netlink_rcv_skb+0x59/0x110
netlink_unicast+0x285/0x3c0
? __alloc_skb+0xdb/0x1a0
netlink_sendmsg+0x20d/0x430
____sys_sendmsg+0x39f/0x3d0
? import_iovec+0x2f/0x40
___sys_sendmsg+0x99/0xe0
__sys_sendmsg+0x8a/0xf0
do_syscall_64+0x81/0x970
? __sys_bind+0xe3/0x110
? syscall_exit_work+0x143/0x1b0
? do_syscall_64+0x244/0x970
? sock_alloc_file+0x63/0xc0
? syscall_exit_work+0x143/0x1b0
? do_syscall_64+0x244/0x970
? alloc_fd+0x12e/0x190
? put_unused_fd+0x2a/0x70
? do_sys_openat2+0xa2/0xe0
? syscall_exit_work+0x143/0x1b0
? do_syscall_64+0x244/0x970
? exc_page_fault+0x7e/0x1a0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
[...]
</TASK>

Fix this by checking is_visible() before trying to touch the attribute.