inetpeer: fix RCU lookup() again

My prior fix was not complete, as we were dereferencing a pointer
three times per node, not twice as I initially thought.

Fixes: 4cc5b44b ("inetpeer: fix RCU lookup()")
Fixes: b145425f ("inetpeer: remove AVL implementation in favor of RB tree")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>