[patch] fix the irq migration

["Siddha, Suresh B" <suresh.b.siddha@intel.com>]

While debugging some other irq migration issue, observed this issue with
-git kernels. Ingo, please ACK it.
---

With the commit 76d2160147f43f982dfe881404cfde9fd0a9da21, irq_chip
default_disable() became an empty function. And with this change, irq
migration in the case of Edge triggered IO-APIC and MSI interrupts happens
with out masking the irq.

Appended patch fixes by using the mask/unmask handlers of irq_chip directly
while doing the irq migration.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

diff --git a/kernel/irq/migration.c b/kernel/irq/migration.c
index 4baa3bb..14ff345 100644
--- a/kernel/irq/migration.c
+++ b/kernel/irq/migration.c
@@ -66,11 +66,11 @@ void move_native_irq(int irq)
 		return;
 
 	if (likely(!(desc->status & IRQ_DISABLED)))
-		desc->chip->disable(irq);
+		desc->chip->mask(irq);
 
 	move_masked_irq(irq);
 
 	if (likely(!(desc->status & IRQ_DISABLED)))
-		desc->chip->enable(irq);
+		desc->chip->unmask(irq);
 }