arm64: dts: bitmain: Add GPIO Line names for Sophon Edge board

Add GPIO line names for Sophon Edge board based on BM1880 SoC from
Bitmain. Line names are based on the board schematics as well as the
96Boards Consumer Edition specification v1.0.

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