fix(cpus): workaround for Cortex-X4 erratum 2897503

Cortex-X4 erratum 2897503 is a Cat B erratum that applies
to all revisions <= r0p1 and is fixed in r0p2.

The workaround is to set CPUACTLR4_EL1[8] to 1.

SDEN documentation:
https://developer.arm.com/documentation/SDEN-2432808/latest

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I3178a890b6f1307b310e817af75f8fdfb8668cc9
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index c55597a..2cbbdd2 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -839,6 +839,10 @@
 # to revisions r0p0 and r0p1 of the Cortex-X4 cpu. It is fixed in r0p2.
 CPU_FLAG_LIST += ERRATA_X4_2816013
 
+# Flag to apply erratum 2897503 workaround on reset. This erratum applies
+# to revisions r0p0 and r0p1 of the Cortex-X4 cpu. It is fixed in r0p2.
+CPU_FLAG_LIST += ERRATA_X4_2897503
+
 # Flag to apply erratum 1922240 workaround during reset. This erratum applies
 # to revision r0p0 of the Cortex-A510 cpu and is fixed in r0p1.
 CPU_FLAG_LIST += ERRATA_A510_1922240