omap: Remove uninitialized warning for gpio.c

Flags is not used on 15xx.
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/gpio.c

@@ -1117,7 +1117,7 @@ static inline void _set_gpio_irqenable(struct gpio_bank *bank, int gpio, int ena
  */
 static int _set_gpio_wakeup(struct gpio_bank *bank, int gpio, int enable)
 {
-	unsigned long flags;
+	unsigned long uninitialized_var(flags);
 
 	switch (bank->method) {
 #ifdef CONFIG_ARCH_OMAP16XX