fix(cpus): workaround for Cortex-A76 erratum 2743102

Cortex-A76 erratum 2743102 is a Cat B erratum that applies to
all revisions <=r4p1 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/SDEN885749/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: Ie2cd73bd91417d30b5633d80b2fbee32944bc2de
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index f53bad1..eb6d20f 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -287,6 +287,10 @@
 # only to revisions r3p0 - r4p1 of the Cortex A76 cpu.
 ERRATA_A76_1946160	?=0
 
+# Flag to apply erratum 2743102 workaround during powerdown. This erratum
+# applies to all revisions <= r4p1 of the Cortex A76 cpu and is still open.
+ERRATA_A76_2743102	?=0
+
 # Flag to apply erratum 1508412 workaround during reset. This erratum applies
 # only to revision <= r1p0 of the Cortex A77 cpu.
 ERRATA_A77_1508412	?=0
@@ -916,6 +920,10 @@
 $(eval $(call assert_boolean,ERRATA_A76_1946160))
 $(eval $(call add_define,ERRATA_A76_1946160))
 
+# Process ERRATA_A76_2743102 flag
+$(eval $(call assert_boolean,ERRATA_A76_2743102))
+$(eval $(call add_define,ERRATA_A76_2743102))
+
 # Process ERRATA_A77_1508412 flag
 $(eval $(call assert_boolean,ERRATA_A77_1508412))
 $(eval $(call add_define,ERRATA_A77_1508412))