Workaround for Cortex A78 erratum 1951500

Cortex A78 erratum 1951500 is a Cat B erratum that applies to revisions
r0p0, r1p0, and r1p1.  The workaround is to insert a DMB ST before
acquire atomic instructions without release semantics.  This workaround
works on revisions r1p0 and r1p1, in r0p0 there is no workaround.

SDEN can be found here:
https://documentation-service.arm.com/static/5fb66157ca04df4095c1cc2e

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I47610cee75af6a127ea65edc4d5cffc7e6a2d0a3
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index b7dec0b..93b538c 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -298,6 +298,11 @@
 # to revisions r0p0, r1p0, and r1p1 of the A78 cpu.
 ERRATA_A78_1941498	?=0
 
+# Flag to apply erratum 1951500 workaround during reset. This erratum applies
+# to revisions r1p0 and r1p1 of the A78 cpu.  The issue is present in r0p0 as
+# well but there is no workaround for that revision.
+ERRATA_A78_1951500	?=0
+
 # Flag to apply T32 CLREX workaround during reset. This erratum applies
 # only to r0p0 and r1p0 of the Neoverse N1 cpu.
 ERRATA_N1_1043202	?=0
@@ -583,6 +588,10 @@
 $(eval $(call assert_boolean,ERRATA_A78_1941498))
 $(eval $(call add_define,ERRATA_A78_1941498))
 
+# Process ERRATA_A78_1951500 flag
+$(eval $(call assert_boolean,ERRATA_A78_1951500))
+$(eval $(call add_define,ERRATA_A78_1951500))
+
 # Process ERRATA_N1_1043202 flag
 $(eval $(call assert_boolean,ERRATA_N1_1043202))
 $(eval $(call add_define,ERRATA_N1_1043202))