errata: workaround for Cortex A78 errata 1821534

Cortex A78 erratum 1821534 is a Cat B erratum present in r0p0 and
r1p0 of the A78 processor core, it is fixed in r1p1.

SDEN can be found here:
https://documentation-service.arm.com/static/603e3733492bde1625aa8780

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I71057c4b9625cd9edc1a06946b453cf16ae5ea2c
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index fb33346..541a2a2 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -307,6 +307,10 @@
 # well but there is no workaround for that revision.
 ERRATA_A78_1951500	?=0
 
+# Flag to apply erratum 1821534 workaround during reset. This erratum applies
+# to revisions r0p0 and r1p0 of the A78 cpu.
+ERRATA_A78_1821534	?=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
@@ -605,6 +609,10 @@
 $(eval $(call assert_boolean,ERRATA_A78_1951500))
 $(eval $(call add_define,ERRATA_A78_1951500))
 
+# Process ERRATA_A78_1821534 flag
+$(eval $(call assert_boolean,ERRATA_A78_1821534))
+$(eval $(call add_define,ERRATA_A78_1821534))
+
 # Process ERRATA_N1_1043202 flag
 $(eval $(call assert_boolean,ERRATA_N1_1043202))
 $(eval $(call add_define,ERRATA_N1_1043202))