arm64: dts: rockchip: synchronize rk3399 opps with vendor kernel

The vendor-kernel did increase the minimum voltage for some low frequency
opps to 825mV citing stability reasons. So do that in mainline as well
and also use the ranged notation the vendor-kernel switched to, to give
a bit more flexibility for different regulator setups.

Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20210225133322.3420724-1-heiko@sntech.de


Signed-off-by: Heiko Stuebner <heiko@sntech.de>