realtek: remove hardcoded sys-led configurations

realtek: remove hardcoded sys-led configurations

Disabling the sys-led peripheral should be done via a pin controller,
for which pinctrl-single nodes are present in the platform DTSI files.
Drop the hardcoded per-platform sys-led configurations, and require
things to be set up in the devicetree.

Co-developed-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Tested-by: Bjørn Mork <bjorn@mork.no>