pinctrl: microchip-sgpio: return error in spgio_output_set()

Make sgpio_output_set() return an error value. Don't just ignore the
return value of any regmap access but propagate it to our callers. Even
if the accesses never fail, this is a preparation patch to add single
shot mode where we need to poll a bit and thus we might get -ETIMEDOUT.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220226204507.2511633-5-michael@walle.cc


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