ipv6: ndisc: Remove __in6_dev_get() in pndisc_{constructor,destructor}().

ipv6_dev_mc_{inc,dec}() has the same check.

Let's remove __in6_dev_get() from pndisc_constructor() and
pndisc_destructor().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250702230210.3115355-2-kuni1840@gmail.com


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