fix(cpus): workaround for Neoverse V1 errata 2779461

Neoverse V1 erratum 2779461 is a Cat B erratum that applies to
all revisions <=r1p2 and is still open.

The workaround sets CPUACTLR3_EL1[47] bit to 1. Setting this
bit might have a small impact on power and negligible impact
on performance.

SDEN documentation:https://developer.arm.com/documentation/SDEN1401781/latest

Change-Id: I367cda1779684638063d7292fda20ca6734e6f10
Signed-off-by: Sona Mathew <SonaRebecca.Mathew@arm.com>
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 4ae4e54..c4a0e15 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -472,6 +472,10 @@
    CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1 and r1p2 of the
    CPU. It is still open.
 
+-  ``ERRATA_V1_2779461``: This applies erratum 2779461 workaround to Neoverse-V1
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, r1p2 of the
+   CPU. It is still open.
+
 For Cortex-A710, the following errata build flags are defined :
 
 -  ``ERRATA_A710_1987031``: This applies errata 1987031 workaround to