MIPS: DTS: CI20: Fix ACT8600 regulator node names

The Device Tree was using invalid node names for the ACT8600 regulators.
To be fair, it is not the original committer's fault, as the
documentation did gives invalid names as well.

In theory, the fix should have been to modify the driver to accept the
alternative names. However, even though the act8865 driver spits
warnings, the kernel seemed to work fine with what is currently
supported upstream. For that reason, I think it is okay to just update
the DTS.

I removed the "regulator-name" too, since they really didn't bring any
information. The node names are enough.

Fixes: 73f2b940 ("MIPS: CI20: DTS: Add I2C nodes")
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>