pinctrl: mt7622: drop pwm ch7 as mt7622 only has 6 channels

mt7622 is reported by mediatek to have only 6 pwm channels
so drop pindefines for 7th channel

Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Acked-by: Sean Wang <sean.wang@kernel.org>
Link: https://lore.kernel.org/r/20201016204019.2606-4-linux@fw-web.de
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>