Blackfin: increase NR_IRQS beyond NR on-chip IRQs

This makes room for off-chip IRQ controllers.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/include/asm/irq.h b/arch/blackfin/include/asm/irq.h
index e7c0623..89de539 100644
--- a/arch/blackfin/include/asm/irq.h
+++ b/arch/blackfin/include/asm/irq.h
@@ -12,6 +12,9 @@
 
 #include <linux/irqflags.h>
 
+/* IRQs that may be used by external irq_chip controllers */
+#define NR_SPARE_IRQS	32
+
 #include <mach/anomaly.h>
 
 /* SYS_IRQS and NR_IRQS are defined in <mach-bf5xx/irq.h> */