Add support for Cortex-A57 erratum 826974 workaround

Change-Id: I45641551474f4c58c638aff8c42c0ab9a8ec78b4
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 1ed7d14..3ea462b 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -74,6 +74,10 @@
 # only to revision r0p0 of the Cortex A57 cpu.
 ERRATA_A57_813420	?=0
 
+# Flag to apply erratum 826974 workaround during reset. This erratum applies
+# only to revision <= r1p1 of the Cortex A57 cpu.
+ERRATA_A57_826974	?=0
+
 # Process ERRATA_A53_826319 flag
 $(eval $(call assert_boolean,ERRATA_A53_826319))
 $(eval $(call add_define,ERRATA_A53_826319))
@@ -89,3 +93,7 @@
 # Process ERRATA_A57_813420 flag
 $(eval $(call assert_boolean,ERRATA_A57_813420))
 $(eval $(call add_define,ERRATA_A57_813420))
+
+# Process ERRATA_A57_826974 flag
+$(eval $(call assert_boolean,ERRATA_A57_826974))
+$(eval $(call add_define,ERRATA_A57_826974))