[PATCH] gpio_keys: fix struct device declared inside parameter list

A struct device parameter is used in the enable and disable callbacks to
distinguish between different gpio_keys devices.

Platforms that don't use these callbacks may not include struct device
at all, as seen on arch/arm/mach-s3c2410/mach-n30.c

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 include/linux/gpio_keys.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/linux/gpio_keys.h b/include/linux/gpio_keys.h
index b5ca4b2..004ff33 100644
--- a/include/linux/gpio_keys.h
+++ b/include/linux/gpio_keys.h

@@ -1,6 +1,8 @@
 #ifndef _GPIO_KEYS_H
 #define _GPIO_KEYS_H
 
+struct device;
+
 struct gpio_keys_button {
 	/* Configuration parameters */
 	unsigned int code;	/* input event code (KEY_*, SW_*) */

-- 
1.7.5.4