dt-bindings: pinctrl: Add support for Amlogic T7 SoCs

Add a new compatible name for Amlogic T7 pin controller, and add
a new dt-binding header file which document the detail pin names.

Signed-off-by: Huqiang Qin <huqiang.qin@amlogic.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230922094342.637251-2-huqiang.qin@amlogic.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>