[POWERPC] Add missed include

fixes:
arch/powerpc/platforms/pasemi/idle.c: In function 'pasemi_system_reset_exception':
arch/powerpc/platforms/pasemi/idle.c:55: warning: implicit declaration of function 'do_IRQ'
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/platforms/pasemi/idle.c

@@ -22,6 +22,7 @@
 
 #include <linux/kernel.h>
 #include <linux/string.h>
+#include <linux/irq.h>
 
 #include <asm/machdep.h>
 #include <asm/reg.h>