pinctrl: ralink: reintroduce ralink,rt2880-pinmux compatible string

pinctrl: ralink: reintroduce ralink,rt2880-pinmux compatible string

There have been stable releases with the ralink,rt2880-pinmux compatible
string included. Having it removed breaks the ABI. Reintroduce it.

Fixes: e5981cd46183 ("pinctrl: ralink: add new compatible strings for each pinctrl subdriver")
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20230317213011.13656-2-arinc.unal@arinc9.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>