Input: ixp4xx-beeper - fix compile error

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/misc/ixp4xx-beeper.c b/drivers/input/misc/ixp4xx-beeper.c
index d448bb5..3a6ae85c 100644
--- a/drivers/input/misc/ixp4xx-beeper.c
+++ b/drivers/input/misc/ixp4xx-beeper.c
@@ -19,6 +19,7 @@
 #include <linux/input.h>
 #include <linux/delay.h>
 #include <linux/platform_device.h>
+#include <linux/interrupt.h>
 #include <asm/hardware.h>
 
 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");