pinctrl: meson: support amlogic S6/S7/S7D SoC

In some Amlogic SoCs, to save register space or due to some
abnormal arrangements, two sets of pins share one mux register.

A group starting from pin0 is the main pin group, which acquires
the register address through DTS and has management permissions,
but the register bit offset is undetermined.

Another GPIO group as a subordinate group. Some pins mux use share
register and bit offset from bit0 . But this group do not have
register management permissions.

This submission implements this situation.

Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://lore.kernel.org/20250527-s6-s7-pinctrl-v3-3-44f6a0451519@amlogic.com


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