pinctrl: ocelot: fix gpio4 twi function

the TWI function on GPIO4 is actually a multiplexed SCL, not an original
TWI SDA or SCL. Fix it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>