irqchip: gic-v3: Only define gic_peek_irq() when building SMP

irqchip: gic-v3: Only define gic_peek_irq() when building SMP

If building with CONFIG_SMP disbled (for example, with allnoconfig) then
GCC complains that the static function gic_peek_irq() is defined but not
used since the only reference is in the SMP initialisation code. Fix this
by moving the function definition inside the ifdef.

Signed-off-by: Mark Brown <broonie@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1406480224-24628-1-git-send-email-broonie@kernel.org
Signed-off-by: Jason Cooper <jason@lakedaemon.net>