sparse irqs: handle !GENIRQ platforms

Impact: build fix

fix:

 In file included from /home/mingo/tip/arch/m68k/amiga/amiints.c:39:
 /home/mingo/tip/include/linux/interrupt.h:21: error: expected identifier or '('
 /home/mingo/tip/arch/m68k/amiga/amiints.c: In function 'amiga_init_IRQ':

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/random.h b/include/linux/random.h
index ad9daa2..adbf3bd 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -8,6 +8,7 @@
 #define _LINUX_RANDOM_H
 
 #include <linux/ioctl.h>
+#include <linux/irqnr.h>
 
 /* ioctl()'s for the random number generator */
 
@@ -49,7 +50,6 @@
 
 extern struct timer_rand_state *irq_timer_state[];
 
-extern int nr_irqs;
 static inline struct timer_rand_state *get_timer_rand_state(unsigned int irq)
 {
 	if (irq >= nr_irqs)