pinctrl: ralink: rename pinctrl-rt288x to pinctrl-rt2880

pinctrl: ralink: rename pinctrl-rt288x to pinctrl-rt2880

Rename "pinctrl-rt288x.c" to "pinctrl-rt2880.c" as this is the Ralink
RT2880 pinctrl subdriver. Rename PINCTRL_RT288X symbol to PINCTRL_RT2880.
Rename functions that include "rt288x" to "rt2880".

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20220414173916.5552-5-arinc.unal@arinc9.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>