pinctrl: at91-pio4: Enable Push-Pull configuration

Enable push-pull configuration. Remove integer value argument from
open-drain configuration as it is discarded when pinconf function is
called from gpiolib. Add push-pull do debug and get functions.

Signed-off-by: Ryan Wanner <Ryan.Wanner@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/d898c31277f6bce6f7d830edf4332ff605498c7b.1684313910.git.Ryan.Wanner@microchip.com


[Fix two coding style issues]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>