genirq: Reserve the irq when calling irq_set_chip()

The helper macros and functions like for_each_active_irq() don't work
unless the irq is in the allocated_irqs set.

In the case of !CONFIG_SPARSE_IRQ, instead of forcing all users of the
irq infrastructure to explicitly call irq_reserve_irq(), do it for
them.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Cc: ralf@linux-mips.org
LKML-Reference: <1301081931-11240-2-git-send-email-ddaney@caviumnetworks.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/irq/chip.c

@@ -37,6 +37,12 @@ int irq_set_chip(unsigned int irq, struct irq_chip *chip)
 	irq_chip_set_defaults(chip);
 	desc->irq_data.chip = chip;
 	irq_put_desc_unlock(desc, flags);
+	/*
+	 * For !CONFIG_SPARSE_IRQ make the irq show up in
+	 * allocated_irqs. For the CONFIG_SPARSE_IRQ case, it is
+	 * already marked, and this call is harmless.
+	 */
+	irq_reserve_irq(irq);
 	return 0;
 }
 EXPORT_SYMBOL(irq_set_chip);