ARM: at91: fix at91_extern_irq usage for non-dt boards

Since 4b68520dc0ec96153bc0d87bca5ffba508edfcf
ARM: at91: add AIC5 support

we allocate the at91_extern_irq.

This patch makes it static and stores the non-dt extern irq in the soc
structure. It is then possible to use a at91_get_extern_irq() function
to get the value for outside of the irq driver. It is useful for passing
its value to at91_aic_init().

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
[nicolas.ferre@atmel.com: rework commit message]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/mach-at91/soc.h b/arch/arm/mach-at91/soc.h
index 43a225f..a1e1482 100644
--- a/arch/arm/mach-at91/soc.h
+++ b/arch/arm/mach-at91/soc.h
@@ -6,6 +6,7 @@
 
 struct at91_init_soc {
 	int builtin;
+	u32 extern_irq;
 	unsigned int *default_irq_priority;
 	void (*map_io)(void);
 	void (*ioremap_registers)(void);