[IA64] Fix incorrect return value from ia64_setup_msi_irq()

Fix the problem that pci_enable_msi() fails on ia64 platform. The cause of
this problem is incorrect return value of ia64_setup_msi_irq(). It must
return 0 on success, instead of irq number.
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

@@ -109,7 +109,7 @@ int ia64_setup_msi_irq(struct pci_dev *pdev, struct msi_desc *desc)
 	write_msi_msg(irq, &msg);
 	set_irq_chip_and_handler(irq, &ia64_msi_chip, handle_edge_irq);
 
-	return irq;
+	return 0;
 }
 
 void ia64_teardown_msi_irq(unsigned int irq)