[BNX2X]: fix MSI-X/INT#A errata

Errata A0.158 workaround. 

Running in INT#A mode after running with MSI-X fails due to a PCI core
bug.

Signed-off-by: Eliezer Tamir <eliezert@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>