dt-bindings: pinctrl: ralink: add new compatible strings

Add the new compatible strings for mt7620, mt76x8, and rt305x to be able to
properly document the pin muxing information of each SoC, or SoCs that use
the same pinmux data.

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230317213011.13656-9-arinc.unal@arinc9.com


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