mcp23xxx device have configurable 100k pullup resistors. This adds
support for enabling them using pinctrl's pinconf interface.
Signed-off-by: NSebastian Reichel <sebastian.reichel@collabora.co.uk>
Tested-by: NEnric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>