fix(cpus): workaround for Cortex-A78 erratum 2742426

Cortex-A78 erratum 2742426 is a Cat B erratum that applies to
all revisions <= r1p2 and is still open.

The workaround is to set the CPUACTLR5_EL1[56:55] to 2'b01.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1401784/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: I42506a87d41c9e2b30bc78c08d22f36e1f9635c1
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 4582f28..112d8cb 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -357,6 +357,11 @@
 # to revisions r0p0, r1p0, r1p1, and r1p2 of the A78 cpu. It is still open.
 ERRATA_A78_2395406	?=0
 
+# Flag to apply erratum 2742426 workaround during reset. This erratum
+# applies to revisions r0p0, r1p0, r1p1 and r1p2 of the A78 cpu. It is still
+# open.
+ERRATA_A78_2742426	?=0
+
 # Flag to apply erratum 2772019 workaround during powerdown. This erratum
 # applies to revisions r0p0, r1p0, r1p1 and r1p2 of the A78 cpu. It is still
 # open.
@@ -1044,6 +1049,10 @@
 $(eval $(call assert_boolean,ERRATA_A78_2395406))
 $(eval $(call add_define,ERRATA_A78_2395406))
 
+# Process ERRATA_A78_2742426 flag
+$(eval $(call assert_boolean,ERRATA_A78_2742426))
+$(eval $(call add_define,ERRATA_A78_2742426))
+
 # Process ERRATA_A78_2772019 flag
 $(eval $(call assert_boolean,ERRATA_A78_2772019))
 $(eval $(call add_define,ERRATA_A78_2772019))