phonet: Pass net and ifindex to rtm_phonet_notify().

Currently, rtm_phonet_notify() fetches netns and ifindex from dev.

Once route_doit() is converted to RCU, rtm_phonet_notify() will be
called outside of RCU due to GFP_KERNEL, and dev will be unavailable
there.

Let's pass net and ifindex to rtm_phonet_notify().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>