pinctrl: st: stop abusing of_get_named_gpio()

pinctrl: st: stop abusing of_get_named_gpio()

Pin descriptions for this chip only look like standard GPIO device tree
descriptions, while in fact they contain additional data (in excess of
number of cells specified in description of gpio controllers). They also
refer to only pins/gpios belonging to the driver and not to arbitrary
gpio in the system.

Because we want to stop exporting OF-specific handlers from gpiolib-of,
let's parse the pin reference ourself instead of trying to call
of_get_named_gpio().

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/YzSsgoVoJn4+mSpv@google.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>