bnx2x: use the right constant

Nearby code that also tests port suggests that the P0 constant should be
used when port is zero.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e,e1;
@@

* e ? e1 : e1
// </smpl>

Fixes: 6c3218c6

 ("bnx2x: Adjust ETS to 578xx")
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>