tipc: convert to getsockopt_iter

tipc: convert to getsockopt_iter

Convert TIPC sockets (msg, packet, stream proto_ops) to use the new
getsockopt_iter callback with sockopt_t.

Key changes:
- Replace (char __user *optval, int __user *optlen) with sockopt_t *sopt
- Use sopt->optlen for buffer length (input) and returned size (output)
- Use copy_to_iter() instead of put_user()/copy_to_user()

The sockopt_t parameter is named sopt to avoid collision with the
existing optname parameter named opt.

Note: Dropped the unnecessary parentheses to make checkpatch happier.
Also dropped two now-stale comments that referred to the old "res"
variable handling.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260520-getsock_four-v3-6-b8c0b16b7780@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>