qla3xxx: fix warning in drivers/net/qla3xxx.c

this warning:

  drivers/net/qla3xxx.c: In function ‘ql3xxx_probe’:
  drivers/net/qla3xxx.c:3912: warning: ‘pci_using_dac’ may be used uninitialized in this function

triggers because GCC does not recognize the (correct) error flow
between 'pci_using_dac' and 'err'.

Annotate it.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/qla3xxx.c

@@ -3917,7 +3917,7 @@ static int __devinit ql3xxx_probe(struct pci_dev *pdev,
 	struct net_device *ndev = NULL;
 	struct ql3_adapter *qdev = NULL;
 	static int cards_found = 0;
-	int pci_using_dac, err;
+	int uninitialized_var(pci_using_dac), err;
 
 	err = pci_enable_device(pdev);
 	if (err) {