Instead of building the irq-armada-370-xp driver directly when
CONFIG_ARCH_MVEBU is enabled, this commit introduces an intermediate
CONFIG_ARMADA_370_XP_IRQ hidden Kconfig option.

This allows this option to select other interrupt-related Kconfig
options (which will be needed in follow-up commits) rather than having
such selects done from arch/arm/mach-<foo>/.
Signed-off-by: NThomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1455115621-22846-2-git-send-email-thomas.petazzoni@free-electrons.comSigned-off-by: NJason Cooper <jason@lakedaemon.net>