dt-bindings: pinctrl: qcom: Add SM6115 pinctrl bindings

Add device tree binding Documentation details for Qualcomm SM6115 and
SM4250 pinctrl.

Signed-off-by: Iskren Chernev <iskren.chernev@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210723192352.546902-2-iskren.chernev@gmail.com


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