ipv6: mcast: Don't hold RTNL in ipv6_sock_mc_close().

In __ipv6_sock_mc_close(), per-socket mld data is protected by lock_sock(),
and only __dev_get_by_index() and __in6_dev_get() require RTNL.

Let's call __ipv6_sock_mc_drop() and drop RTNL in ipv6_sock_mc_close().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250702230210.3115355-9-kuni1840@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>