pinctrl: sunxi: dt: Consider pin base when calculating bank number from pin

pinctrl: sunxi: dt: Consider pin base when calculating bank number from pin

In prepare_function_table() when the pinctrl function table IRQ entries
are generated, the pin bank is calculated from the absolute pin number;
however the IRQ bank mux array is indexed from the first pin bank of the
controller. For R_PIO controllers, this means the absolute pin bank is
way off from the relative pin bank used for array indexing.

Correct this by taking into account the pin base of the controller.

Fixes: f5e2cd34b12f ("pinctrl: sunxi: allow reading mux values from DT")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/20250607135203.2085226-1-wens@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>