pinctrl: ralink: rename variable names for functions on MT7620 and MT7621

Variables for functions include "grp" on the Ralink MT7620 and MT7621
subdrivers. Rename them to "func" instead as they define the functions for
the pin groups.

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/20220414173916.5552-6-arinc.unal@arinc9.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>