pinctrl: starfive: Serialize adding groups and functions

pinctrl: starfive: Serialize adding groups and functions

The pinctrl dt_node_to_map method may be called in parallel which leads
us to call pinconf_generic_add_group and pinconf_generic_add_function
in parallel. This is not supported though and leads to errors, so add a
mutex to serialize these calls.

Signed-off-by: Jianlong Huang <jianlong.huang@starfivetech.com>
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Link: https://lore.kernel.org/r/20220627085333.1774396-1-emil.renner.berthing@canonical.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>