fix(errata): workaround for Neoverse-N2 erratum 2138953

Neoverse-N2 erratum 2138953 is a Cat B erratum that applies to
revision r0p0 of CPU. It is still open. The workaround
is to write the value 4'b1001 to the PF_MODE bits in the
IMP_CPUECTLR2_EL1 register which will place the data prefetcher
in the most conservative mode instead of disabling it.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1982442/latest

Signed-off-by: nayanpatel-arm <nayankumar.patel@arm.com>
Change-Id: Ife0a4bece7ccf83cc99c1d5f5b5a43084bb69d64
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 6103a5a..1d470e2 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -441,6 +441,10 @@
 # to revision r0p0 of the Neoverse N2 cpu and is still open.
 ERRATA_N2_2138956	?=0
 
+# Flag to apply erratum 2138953 workaround during reset. This erratum applies
+# to revision r0p0 of the Neoverse N2 cpu and is still open.
+ERRATA_N2_2138953	?=0
+
 # Flag to apply erratum 2055002 workaround during reset. This erratum applies
 # to revision r1p0, r2p0 of the Cortex-A710 cpu and is still open.
 ERRATA_A710_2055002	?=0
@@ -822,6 +826,10 @@
 $(eval $(call assert_boolean,ERRATA_N2_2138956))
 $(eval $(call add_define,ERRATA_N2_2138956))
 
+# Process ERRATA_N2_2138953 flag
+$(eval $(call assert_boolean,ERRATA_N2_2138953))
+$(eval $(call add_define,ERRATA_N2_2138953))
+
 # Process ERRATA_A710_2055002 flag
 $(eval $(call assert_boolean,ERRATA_A710_2055002))
 $(eval $(call add_define,ERRATA_A710_2055002))