pinctrl: ocelot: add pwm output option for LAN966x

According to the reference manual, you can mux the PWM output on GPIO27
and GPIO51. This was missing in the pinmux table. Add it.

Tested on a LAN9668 on GPIO51.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220326192848.2944519-1-michael@walle.cc


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>