dt-bindings: pinctrl: qcom,pmic-mpp: Document PM8226 compatible

Document the Device Tree binding for PM8226 MPPs.

Signed-off-by: Rayyan Ansari <rayyan@ansari.sh>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220124171538.18088-1-rayyan@ansari.sh


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