pinctrl: sunxi: number gpio ranges starting from 0

pinctrl: sunxi: number gpio ranges starting from 0

The pinctrl-sunxi driver originally used the pin number as the gpio
range offset. This resulted in large, bogus gpio numbers for the
new sun6i-a31-r pinctrl devices.

This patch makes the driver number the gpios ranges starting from an
offset of 0, by subtracting the pin_base number from the pin number.
This also makes the system-wide gpio number match the pin number.

Tested on sun8i with sysfs exported gpios.

This patch also changes the GPIO bindings for R_PIO:

    gpios = <&r_pio B N flag>;

Where B originally was the pinbank label (L or M) counted from A,
with this patch it becomes (L or M) counted from its pinbank base (L).

Thus

    gpios = <&r_pio 10 11 0>; /* PL11 */

becomes

    gpios = <&r_pio 0 11 0>; /* PL11 */

IMO this is correct, as the binding shows the bank offset and pin offset
within the bank for the GPIO controller. But I'm worried it might be a
bit confusing.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>