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
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 3029458..2a47abe 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -296,6 +296,10 @@
    CPU. This needs to be enabled for revisions r1p0, r1p1, and r1p2. The issue
    is present in r0p0 but there is no workaround. It is still open.
 
+-  ``ERRATA_A78_2376745``: This applies errata 2376745 workaround to Cortex-A78
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, and r1p2, and
+   it is still open.
+
 For Cortex-A78 AE, the following errata build flags are defined :
 
 - ``ERRATA_A78_AE_1941500`` : This applies errata 1941500 workaround to