dt-bindings: pinctrl: qcom,pmic-gpio: document pm8550, pm8550b, pm8550ve, pm8550vs, pmk8550 & pmr735d

Document compatible, pin count & pin names for pm8550, pm8550b, pm8550ve,
pm8550vs, pmk8550 & pmr735d SPMI GPIO controllers.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221114-narmstrong-sm8550-upstream-spmi-v2-2-b839bf2d558a@linaro.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>