alpha: irq clean up

Stop touching irq_desc[irq] directly, instead use accessor
functions provided. Use irq_has_action instead of directly
testing the irq_desc.

Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>
diff --git a/arch/alpha/kernel/sys_titan.c b/arch/alpha/kernel/sys_titan.c
index ffa48e8..9870f3d 100644
--- a/arch/alpha/kernel/sys_titan.c
+++ b/arch/alpha/kernel/sys_titan.c
@@ -139,7 +139,7 @@
 static void
 titan_end_irq(unsigned int irq)
 {
-	if (!(irq_desc[irq].status & (IRQ_DISABLED|IRQ_INPROGRESS)))
+	if (!(irq_to_desc(irq)->status & (IRQ_DISABLED|IRQ_INPROGRESS)))
 		titan_enable_irq(irq);
 }
 
@@ -189,7 +189,7 @@
 {
 	long i;
 	for (i = imin; i <= imax; ++i) {
-		irq_desc[i].status |= IRQ_LEVEL;
+		irq_to_desc(i)->status |= IRQ_LEVEL;
 		set_irq_chip_and_handler(i, ops, alpha_do_IRQ);
 	}
 }