arm64: dts: bitmain: Add GPIO support for BM1880 SoC

Add GPIO support for Bitmain BM1880 SoC based on Designware APB GPIO
controller IP. IP exposes 3 GPIO controllers with a total of 72 pins.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>