* Explicitly set vdd_log voltage for NanoPi M4V2 - possibly fix stability issues
* Regulator tweaks for NanoPi M4V2
* Add vdd_log to kernel and switch vdd_center back to 900mV
* Switch vdd_center to 0.95
* Make rk80x bucks voltage steps shorter to make the NanoPi M4V2 stable
* Tweak u-boot config for NanoPi M4V2
* Made the rk808 voltage steps configurable and configured 50mV for NanoPi M4V2