The 'regulator-init-microvolt' property is not currently supported by
any driver, it was simply carried on from downstream kernels.
The problem is also indicated by the following dtbs_check warning:
rk3588-rock-5b.dtb: pmic@0: regulators:dcdc-reg4: Unevaluated properties are not allowed ('regulator-init-microvolt' was unexpected)
Remove the invalid property from all affected DTS files.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>