dt-bindings: pinctrl: qcom,pmic-gpio: describe gpio-line-names

Add missing 'gpio-line-names' property and describe its constraints for
all models except PM8226 (which seems not really used).

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220507194913.261121-4-krzysztof.kozlowski@linaro.org


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