dt-bindings: pinctrl: npcm8xx: add missing pin group and mux function

Add the following missing pin group and mux function:
smb6b, smb6c, smb6d, smb7b, smb7c, smb7d, bu4, bu4b, bu5, bu5b, bu6,
gpo187.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/20240630090104.565779-1-tmaimon77@gmail.com


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