pinctrl: starfive: Reset pinmux settings

pinctrl: starfive: Reset pinmux settings

Current u-boot doesn't seem to take into account that some GPIOs are
configured as inputs/outputs of certain peripherals on power-up. This
means it ends up configuring some GPIOs as inputs to more than one
peripheral which the documentation explicitly says is illegal. Similarly
it also ends up configuring more than one GPIO as output of the same
peripheral. While not explicitly mentioned by the documentation this
also seems like a bad idea.

The easiest way to remedy this mess is to just disconnect all GPIOs from
peripherals and have our pinmux configuration set everything up
properly. This, however, means that we'd disconnect the serial console
from its pins for a while, so add a device tree property to keep
certain GPIOs from being reset.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>