dt-bindings: pinctrl: Add compatibles for Amlogic C3 SoCs

Add a new compatible name for Amlogic C3 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>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230714122441.3098337-2-huqiang.qin@amlogic.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>