gpio: Add G7 Aspeed gpio controller driver

In the 7th generation of the SoC from Aspeed, the control logic of the
GPIO controller has been updated to support per-pin control. Each pin now
has its own 32-bit register, allowing for individual control of the pin’s
value, direction, interrupt type, and other settings.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>