pinctrl: sx150x: support setting multiple pins at once

If the chip does not have an oscio pin, all pins are configured in
the same regmap register making it trivial to update all pins at
once, so do that. If an oscio pin is present, there needs to be
more locking in place to handle all cases correctly, so this is
skipped.

Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>