pinctrl: ralink: rename MT7628(an) functions to MT76X8

The functions that include "MT7628(an)" are for MT7628 and MT7688 SoCs.
Rename them to MT76X8 to refer to both of the SoCs.
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/20220414173916.5552-2-arinc.unal@arinc9.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>