ARM: dts: sun7i: Add regulator configuration for pcDuino v3 Nano

The power configuration on this board is the same as the pcDuino v3.
This will enable frequency/voltage scaling over the standard A20
operating points from 144 MHz to 960 MHz.

Tested using cpufreq-ljt-stress-test on two pcDuino v3 Nano boards; also
tested successfully with voltages reduced by 0.025 V.

Signed-off-by: Adam Sampson <ats@offog.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>