packet: minor: convert status bits into shifting format

This makes it more readable and clearer what bits are still free to
use. The compiler reduces this to a constant for us anyway.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>