pinctrl: qcom: lpass-lpi: split slew rate set to separate function

pinctrl: qcom: lpass-lpi: split slew rate set to separate function

Setting slew rate for each pin will grow with upcoming Qualcomm SoCs,
so split the code responsible for this into separate function for easier
readability and maintenance.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20231013145935.220945-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>