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>