The Nintendo NES/SuperNES features an R16 already well supported in
mainline.

The console over UART0 may be wired on two ports of the R16, both
available on the NES Classic PCB.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>