dt-bindings: pinctl: amlogic,pinctrl-a4: Add compatible string for S7/S7D/S6

Update dt-binding document for pinctrl of Amlogic S7/S7D/S6.

Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/20250527-s6-s7-pinctrl-v3-1-44f6a0451519@amlogic.com


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