arm64: dts: qcom: msm8998: Make regulator voltages multiple of step-size

These voltages are not a multiple of the given step-size 8000 (with base
voltage 1664000) in pm8998_pldo, resulting in PLDO regulators l18 and
l22 failing to validate and in turn not probing the rpm-pm8998-regulator
driver:

    l18: unsupportable voltage constraints 2856000-2848000uV
    qcom_rpm_smd_regulator rpm-glink:rpm-requests:pm8998-regulators: l18: devm_regulator_register() failed, ret=-22

Round the voltages down for the sake of erring on the safe side, leaving
a comment in place to document this discrepancy wrt downstream sources.

Fixes: 390883af ("arm64: dts: qcom: msm8998: Introduce support for Sony Yoshino platform")
Reported-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220507153627.1478268-1-marijn.suijten@somainline.org

arch/arm64/boot/dts/qcom/msm8998-sony-xperia-yoshino-poplar.dts

@@ -26,11 +26,13 @@ &lab {
 };
 
 &vreg_l18a_2p85 {
-	regulator-min-microvolt = <2850000>;
-	regulator-max-microvolt = <2850000>;
+	/* Note: Round-down from 2850000 to be a multiple of PLDO step-size 8000 */
+	regulator-min-microvolt = <2848000>;
+	regulator-max-microvolt = <2848000>;
 };
 
 &vreg_l22a_2p85 {
-	regulator-min-microvolt = <2700000>;
-	regulator-max-microvolt = <2700000>;
+	/* Note: Round-down from 2700000 to be a multiple of PLDO step-size 8000 */
+	regulator-min-microvolt = <2696000>;
+	regulator-max-microvolt = <2696000>;
 };