pinctrl: hide CONFIG_PINMUX and CONFIG_PINCONF

These symbols are supposed to be selected by the drivers actually needing
them. The only situation where it would make sense to enable them without a
driver selecting them is when an out-of-tree pinctrl driver is used or
for compile testing.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>