net: smc91x: Remove an unused variable

Commit cb6e0b36 ("net: smc91x: make use of 4th parameter to devm_gpiod_get_index")
caused the following build warning:

drivers/net/ethernet/smsc/smc91x.c:2208:6: warning: unused variable 'res' [-Wunused-variable]

Remove the unused 'res' variable.
Reported-by: Olof's autobuilder <build@lixom.net>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/smsc/smc91x.c

@@ -2205,7 +2205,6 @@ static int try_toggle_control_gpio(struct device *dev,
 {
 	struct gpio_desc *gpio = *desc;
 	enum gpiod_flags flags = value ? GPIOD_OUT_LOW : GPIOD_OUT_HIGH;
-	int res;
 
 	gpio = devm_gpiod_get_index_optional(dev, name, index, flags);
 	if (IS_ERR(gpio))