pinctrl: sunxi: change irq_bank_base to irq_bank_map

The Allwinner H6 SoC have its pin controllers with the first IRQ-capable
GPIO bank at IRQ bank 1 and the second bank at IRQ bank 5.

Change the current code that uses IRQ bank base to a IRQ bank map, in
order to support the case that holes exist among IRQ banks.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>