gpiolib: of: add a quirk for legacy names in Mediatek mt2701-cs42448

The driver is using non-standard "i2s1-in-sel-gpio1" and
"i2s1-in-sel-gpio2" names to describe its gpios. In preparation to
converting to the standard naming (i2s1-in-sel-gpios) and switching the
driver to gpiod API add a quirk to gpiolib to keep compatibility with
existing DTSes.

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>