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

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

pinctrl-rt2880.c and pinmux.h make up the Ralink pinctrl driver. Rename
pinctrl-rt2880.c to pinctrl-ralink.c. Rename pinmux.h to pinctrl-ralink.h.
Fix references to it. Rename functions that include "rt2880" to "ralink".

Remove PINCTRL_RT2880 symbol and make the existing PINCTRL_RALINK symbol
compile pinctrl-ralink.c. Change the bool to "Ralink pinctrl driver".

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/20220414173916.5552-3-arinc.unal@arinc9.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>