[IA64] genirq fixup for SGI/SN

This patch allows the system to boot and enables the console and at least
some hardware drivers, as well as some platform error handling.

Tested on a variety of SGI Altix system without issues.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Tested-by: Raymund Will <rw@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/sn/kernel/irq.c b/arch/ia64/sn/kernel/irq.c
index dfac09a..62cf4dd 100644
--- a/arch/ia64/sn/kernel/irq.c
+++ b/arch/ia64/sn/kernel/irq.c
@@ -352,6 +352,8 @@
 	spin_lock(&sn_irq_info_lock);
 	list_add_rcu(&sn_irq_info->list, sn_irq_lh[sn_irq_info->irq_irq]);
 	reserve_irq_vector(sn_irq_info->irq_irq);
+	if (sn_irq_info->irq_int_bit != -1)
+		irq_set_handler(sn_irq_info->irq_irq, handle_level_irq);
 	spin_unlock(&sn_irq_info_lock);
 
 	register_intr_pda(sn_irq_info);