genirq: keep affinities set from userspace across free/request_irq()

Impact: preserve user-modified affinities on interrupts

Kumar Galak noticed that commit
1840475676 (genirq: Expose default irq
affinity mask (take 3))

overrides an already set affinity setting across a free /
request_irq(). Happens e.g. with ifdown/ifup of a network device.

Change the logic to mark the affinities as set and keep them
intact. This also fixes the unlocked access to irq_desc in
irq_select_affinity() when called from irq_affinity_proc_write()

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/irq/migration.c

@@ -1,17 +1,6 @@
 
 #include <linux/irq.h>
 
-void set_pending_irq(unsigned int irq, cpumask_t mask)
-{
-	struct irq_desc *desc = irq_to_desc(irq);
-	unsigned long flags;
-
-	spin_lock_irqsave(&desc->lock, flags);
-	desc->status |= IRQ_MOVE_PENDING;
-	desc->pending_mask = mask;
-	spin_unlock_irqrestore(&desc->lock, flags);
-}
-
 void move_masked_irq(int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);