powerpc/5200: Build fix for mpc52xx watchdog timer code

mpc52xx_gpt_wdt_setup is defined as 0, which causes the following build
failure with gcc 4.5, since it's built with -Werror.

arch/powerpc/platforms/52xx/mpc52xx_gpt.c:761:3: error: statement with no effect

Changing it to a static inline fixes the problem.
Reported-by: NJeff Mahoney <jeffm@suse.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

arch/powerpc/platforms/52xx/mpc52xx_gpt.c

@@ -711,7 +711,11 @@ static int __devinit mpc52xx_gpt_wdt_init(void)
 	return 0;
 }
 
-#define mpc52xx_gpt_wdt_setup(x, y)		(0)
+static inline int mpc52xx_gpt_wdt_setup(struct mpc52xx_gpt_priv *gpt,
+					const u32 *period)
+{
+	return 0;
+}
 
 #endif	/*  CONFIG_MPC5200_WDT	*/