pinctrl: sunxi: fix wrong irq_banks number for H5 pinctrl

The pin controller of Allwinner H5 has three IRQ banks, however in old
versions of drivers and device trees, only two are set, which makes
PG bank IRQ not available.

If it's directly set to 3, the old device trees will fail to boot.

Add a workaround (and a warning) for older device trees, and allow new
device trees to use correct 3 IRQ banks.

Fixes: 838adb57 ("drivers: pinctrl: add driver for Allwinner H5 SoC")
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>