fix(cpus): workaround for Neoverse V1 erratum 2743093

Neoverse V1 erratum 2743093 is a Cat B erratum that applies to
all revisions <=r1p2 and is still open. The workaround is to
insert a dsb before the isb in the power down sequence.

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

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: I8ee7c16c14c4fd6ee35d20c855273ecfce0d1b32
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index c07a0aa..ac2db09 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -460,6 +460,10 @@
    CPU. This needs to be enabled for revisions r0p0, r1p0 and r1p1 of the CPU.
    It is still open.
 
+-  ``ERRATA_V1_2743093``: This applies errata 2743093 workaround to Neoverse-V1
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1 and 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