ARM: at91: sparse irq support

Enable sparse irq support for multisoc image. It involves to add the
NR_IRQS_LEGACY offset to static SoC irq number definitions since NR_IRQS_LEGACY
irq descs are allocated before AIC requests irq descs allocation.
Move NR_AIC_IRQS macro to a more appropiate place with the purpose to
remove mach/irqs.h later.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
index e401dea..7d0c40a 100644
--- a/arch/arm/mach-at91/Kconfig
+++ b/arch/arm/mach-at91/Kconfig
@@ -30,6 +30,7 @@
 	bool
 	select CPU_ARM926T
 	select MULTI_IRQ_HANDLER
+	select SPARSE_IRQ
 	select AT91_SAM9_TIME
 	select AT91_SAM9_SMC