ARM: mmp: support DT in irq

Merge irq-pxa168 and irq-mmp2. And support device tree also.

Since CONFIG_SPARSE_IRQ is enabled in arch-mmp, base irq starts from
NR_IRQS_LEGACY.

Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index cf006d4..4cf9d42 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -632,6 +632,7 @@
 	select CLKDEV_LOOKUP
 	select GENERIC_CLOCKEVENTS
 	select GPIO_PXA
+	select IRQ_DOMAIN
 	select TICK_ONESHOT
 	select PLAT_PXA
 	select SPARSE_IRQ