[IA64] Fix possible invalid memory access in ia64_setup_msi_irq()

The following 'if' statement in ia64_setup_msi_irq() always fails even
if create_irq() returns <0 value, because variable 'irq' is defined as
unsigned int. It would cause invalid memory access.

        irq = create_irq();
        if (irq < 0)
                return irq;
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/msi_ia64.c

@@ -68,7 +68,7 @@ int ia64_setup_msi_irq(struct pci_dev *pdev, struct msi_desc *desc)
 {
 	struct msi_msg	msg;
 	unsigned long	dest_phys_id;
-	unsigned int	irq, vector;
+	int	irq, vector;
 
 	irq = create_irq();
 	if (irq < 0)