isdn: hisax: Fix pnp_irq's error checking for setup_elsa_isapnp

The pnp_irq() function returns -1 if an error occurs.
pnp_irq() error checking for zero is not correct.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/hisax/elsa.c

@@ -945,7 +945,7 @@ static int setup_elsa_isapnp(struct IsdnCard *card)
 					card->para[1] = pnp_port_start(pnp_d, 0);
 					card->para[0] = pnp_irq(pnp_d, 0);
 
-					if (!card->para[0] || !card->para[1]) {
+					if (card->para[0] == -1 || !card->para[1]) {
 						printk(KERN_ERR "Elsa PnP:some resources are missing %ld/%lx\n",
 						       card->para[0], card->para[1]);
 						pnp_disable_dev(pnp_d);