phonet: Pass ifindex to fill_addr().

We will convert addr_doit() and getaddr_dumpit() to RCU, both
of which call fill_addr().

The former will call phonet_address_notify() outside of RCU
due to GFP_KERNEL, so dev will not be available in fill_addr().

Let's pass ifindex directly to fill_addr().

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