The previous fix made the TVC clock get muxed in on the
D-Link DIR-685 instead of giving nagging warnings of this
not working. Not good. We didn't want that, as it breaks
video.

Create a specific group for the TVC CLK, and break out
a specific GPIO group for it on the SL3516 so we can use
that line as GPIO if we don't need the TVC CLK.

Fixes: d17f477c

 ("pinctrl: gemini: Mask and set properly")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>