gpio: it87: remove unused code

Fix the following clang warning:

drivers/gpio/gpio-it87.c:128:20: warning: unused function 'superio_outw'
[-Wunused-function].

Reported-by: Abaci Robot <[e-mail]>
Signed-off-by: Jiapeng Chong <[e-mail]>
Acked-by: Simon Guinot <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-it87.c

···
 	return val;
 }
 
-static inline void superio_outw(int val, int reg)
-{
-	outb(reg++, REG);
-	outb(val >> 8, VAL);
-	outb(reg, REG);
-	outb(val, VAL);
-}
-
 static inline void superio_set_mask(int mask, int reg)
 {
 	u8 curr_val = superio_inb(reg);