arm64: dts: meson-g12b: add cpus OPP tables

arm64: dts: meson-g12b: add cpus OPP tables

Add the OPP table taken from the HardKernel Odroid-N2 DTS.

The Amlogic G12B SoC seems to available in 2 types :
- low-speed: Cortex-A73 Cluster up to 1,704GHz
- high-speed: Cortex-A73 Cluster up to 2.208GHz

The Cortex-A73 Cluster can be clocked up to 1,896GHz for both types.

The Vendor Amlogic A311D OPP table are slighly different, with lower
voltages than the HardKernel S922X tables but seems to be high-speed type.

This adds the conservative OPP table with the S922X higher voltages
and the maximum low-speed OPP frequency.

The values were tested to be stable on an HardKernel Odroid-N2 board
running the arm64 cpuburn at [1] and cycling between all the possible
cpufreq translations for both clusters and checking the final frequency
using the clock-measurer, script at [2].

[1] https://github.com/ssvb/cpuburn-arm/blob/master/cpuburn-a53.S
[2] https://gist.github.com/superna9999/d4de964dbc0f84b7d527e1df2ddea25f

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>