gpio: tegra: add stub set_debounce callback

gpiolib spits out error messages if the underlying
driver does not implement the set_debounce api.

Add stub api since Tegra does not support
gpio debounce in hardware.

Bug 924471

Change-Id: Iadd4ddb41a3a028edf7d55fccf100c8d4bcb5fa2
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>
Reviewed-on: http://git-master/r/75639
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>

drivers/gpio/gpio-tegra.c

@@ -202,14 +202,19 @@ static int tegra_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
 	return 0;
 }
 
-
+static int tegra_gpio_set_debounce(struct gpio_chip *chip, unsigned offset,
+					int value)
+{
+	return -ENOSYS;
+}
 
 static struct gpio_chip tegra_gpio_chip = {
 	.label			= "tegra-gpio",
 	.direction_input	= tegra_gpio_direction_input,
 	.get			= tegra_gpio_get,
 	.direction_output	= tegra_gpio_direction_output,
 	.set			= tegra_gpio_set,
+	.set_debounce		= tegra_gpio_set_debounce,
 	.base			= 0,
 	.ngpio			= TEGRA_NR_GPIOS,
 };