PVTM use "cpu-supply" as the name of regulator to get PVTM value to
select opp level, but old dts use "cpu0-supply" as the name of cpu,
so we need be compatible with the old regulator name of cpu.
Change-Id: Id6dbb0b4a85e6154b9be38ffb373e7eab7199781
Signed-off-by: Liang Chen <cl@rock-chips.com>