x86_64: rename irq_desc/irq_desc_alloc

change names:

          irq_desc() ==> irq_desc_alloc
	__irq_desc() ==> irq_desc

Also split a few of the uses in lowlevel x86 code.

v2: need to check if desc is null in smp_irq_move_cleanup

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index f337f87..5d5976e 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -83,7 +83,7 @@
 
 	if (i < nr_irqs) {
 		unsigned any_count = 0;
-		struct irq_desc *desc = __irq_to_desc(i);
+		struct irq_desc *desc = irq_to_desc(i);
 
 		if (!desc)
 			return 0;
@@ -206,7 +206,7 @@
 	stack_overflow_check(regs);
 #endif
 
-	desc = __irq_to_desc(irq);
+	desc = irq_to_desc(irq);
 	if (likely(desc))
 		generic_handle_irq_desc(irq, desc);
 	else {