gpio: mockup: remove unused variable gc

The variable gc is assigned but never read and is redundant. Remove it.
Cleans up clang warning:

drivers/gpio/gpio-mockup.c:169:2: warning: Value stored to 'gc' is never read

Signed-off-by: Colin Ian King <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-mockup.c

···
 	struct gpio_mockup_chip *chip;
 	struct seq_file *sfile;
 	struct gpio_desc *desc;
-	struct gpio_chip *gc;
 	int rv, val;
 
 	rv = kstrtoint_from_user(usr_buf, size, 0, &val);
···
 	priv = sfile->private;
 	desc = priv->desc;
 	chip = priv->chip;
-	gc = &chip->gc;
 
 	gpiod_set_value_cansleep(desc, val);
 	irq_sim_fire(&chip->irqsim, priv->offset);