bna: Fix warning false positive.

GCC can't see that in all non-error-return paths we do in fact
set *using_dac to something.

Add an explicit initialization to remove this warning:

drivers/net/ethernet/brocade/bna/bnad.c: In function ‘bnad_pci_probe’:
drivers/net/ethernet/brocade/bna/bnad.c:3079:5: warning: ‘using_dac’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/net/ethernet/brocade/bna/bnad.c:3233:7: note: ‘using_dac’ was declared here
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/brocade/bna/bnad.c

@@ -3268,6 +3268,7 @@ bnad_pci_probe(struct pci_dev *pdev,
 	 *	Output : using_dac = 1 for 64 bit DMA
 	 *			   = 0 for 32 bit DMA
 	 */
+	using_dac = false;
 	err = bnad_pci_init(bnad, pdev, &using_dac);
 	if (err)
 		goto unlock_mutex;