riscv: cpu: jh7110: Add gpio helper macros

Add gpio.h header file that includes JH7110 helper macros. The file is
imported from StarFive github[1] with small changes such as alignment.

[1]: https://github.com/starfive-tech/u-boot



Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>