irqchip/gic: Kconfig the number of instances

There is currently a hack in the GIC driver making it possible
to pass the number of GIC instances from the platform-specific
include files and thus override the variable MAX_GIC_NR.

With multiplatform deployments, this will not work as we need
to get rid of the platform-specific include files.

It turns out that this feature is only used by the RealView
platform which has a cascaded GIC. So move the configuration
to Kconfig and bump to 2 instances if we're building for the
RealView. The include file hacks can then be removed.

Tested on the ARM PB11MPCore with its cascaded GIC.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 4d7294e..bf29a8b 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -8,6 +8,11 @@
 	select IRQ_DOMAIN_HIERARCHY
 	select MULTI_IRQ_HANDLER
 
+config ARM_GIC_MAX_NR
+	int
+	default 2 if ARCH_REALVIEW
+	default 1
+
 config ARM_GIC_V2M
 	bool
 	depends on ARM_GIC