genirq: export irq_chip_set_wake_parent symbol

Export the irq_chip_set_wake_parent symbol so that drivers with
hierarchical IRQ chips can be built as a module.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Reported-by: Mark Brown <broonie@kernel.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>