juno/dvfs: Fix performance domain names

The perfomance domain names for Juno R1 & R2 are
not correctly set and aligned with the ones for
Juno R0.

Change-Id: Id6b91499eebf59a0ed8f0b8edebd9d8072472b50
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>