fix(cpus): workaround for Cortex X3 erratum 2743088

Cortex X3 erratum 2743088 is a Cat B erratum that applies to all
revisions <= r1p1 and is fixed in r1p2. The workaround is to add a DSB
instruction before the ISB of the powerdown code sequence specified in
the TRM.

SDEN documentation: https://developer.arm.com/documentation/2055130

Change-Id: I2c8577e3ca0781af8b1c3912e577d3bd77f92709
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index bbf44b4..701356d 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -777,6 +777,10 @@
 # to revisions r0p0, r1p0 and r1p1 of the Cortex-X3 cpu, it is fixed in r1p2.
 CPU_FLAG_LIST += ERRATA_X3_2742421
 
+# Flag to apply erratum 2743088 workaround on powerdown. This erratum applies
+# to revisions r0p0, r1p0 and r1p1 of the Cortex-X3 cpu, it is fixed in r1p2.
+CPU_FLAG_LIST += ERRATA_X3_2743088
+
 # Flag to apply erratum 2779509 workaround on reset. This erratum applies
 # to revisions r0p0, r1p0, r1p1 of the Cortex-X3 cpu, it is fixed in r1p2.
 CPU_FLAG_LIST += ERRATA_X3_2779509