scripts: genpinctrl: add support for ethernet pins

Add support for ethernet pins.

F1 settings taken from RM0008 Rev 20, Table 209.
Other series settings are taken from current Zephyr settings. Note that
they will likely need to be adjusted, as very-high-speed is not needed
for all signals.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>