fix(errata): workaround for Cortex-A78 erratum 2376745

Cortex-A78 erratum 2376745 is a cat B erratum that applies to revisions
r0p0 - r1p2 and is still open. The workaround is to set bit[0] of
CPUACTLR2 which will force PLDW/PFRM ST to behave like PLD/PRFM LD and
not cause invalidation to other PE caches.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1401784



Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I6f1a3a7d613c5ed182a7028f912e0f6ae3aa7f98