pinctrl: bcm2835: Implement bcm2711_pinconf_get

The BCM2711 allows to read the bias config. So implement pin_conf_get
accordingly. The pull resistor values has been taken from the
BCM2711/7211 datasheet.

This implementation assumes that BCM7211 behaves the same way.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Message-ID: <20240307070113.4888-3-wahrenst@gmx.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>