fix(cpus): workaround for Neoverse N2 erratum 2743089

Neoverse N2 erratum 2743089 is a Cat B erratum that applies to
all revisions <=r0p2 and is fixed in r0p3. The workaround is to
insert a dsb before the isb in the power down sequence.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1982442/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: Idec862226bd32c91374a8bbd5d73d7ee480a34d9
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index e56eac1..9311420 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -574,6 +574,10 @@
    CPU. This needs to be enabled for revision r0p0 of the CPU, it is fixed in
    r0p1.
 
+-  ``ERRATA_N2_2743089``: This applies errata 2743089 workaround to Neoverse-N2
+   CPU. This needs to be enabled for revisions r0p0, r0p1 and r0p2. It is fixed
+   in r0p3.
+
 For Cortex-X2, the following errata build flags are defined :
 
 -  ``ERRATA_X2_2002765``: This applies errata 2002765 workaround to Cortex-X2