ARM: SAMSUNG: Initialize PWM backlight enable_gpio field

The GPIO API defines 0 as being a valid GPIO number, so this field needs
to be initialized explicitly.

Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/mach-s3c64xx/mach-smdk6410.c

@@ -625,6 +625,7 @@ static struct samsung_bl_gpio_info smdk6410_bl_gpio_info = {
 
 static struct platform_pwm_backlight_data smdk6410_bl_data = {
 	.pwm_id = 1,
+	.enable_gpio = -1,
 };
 
 static struct s3c_hsotg_plat smdk6410_hsotg_pdata;