fix(errata): workaround for Cortex-A710 erratum 2008768

Cortex-A710 erratum 2008768 is a Cat B erratum that applies to revisions
r0p0, r1p0, and r2p0, and is fixed in r2p1. The workaround is to clear
the ED bit in each ERXCTLR_EL1 register before setting the PWRDN bit in
CPUPWRCTLR_EL1.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1775101

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Ib2171c06da762dd4155b02c03d86766f1616381d
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 462ca9d..fe98a30 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -484,6 +484,10 @@
 # to revision r0p0, r1p0 and r2p0 of the Cortex-A710 cpu and is fixed in r2p1.
 ERRATA_A710_2282622	?=0
 
+# Flag to apply erratum 2008768 workaround during reset. This erratum applies
+# to revision r0p0, r1p0 and r2p0 of the Cortex-A710 cpu and is fixed in r2p1.
+ERRATA_A710_2008768	?=0
+
 # Flag to apply erratum 2067956 workaround during reset. This erratum applies
 # to revision r0p0 of the Neoverse N2 cpu and is still open.
 ERRATA_N2_2067956	?=0
@@ -990,6 +994,10 @@
 $(eval $(call assert_boolean,ERRATA_A710_2282622))
 $(eval $(call add_define,ERRATA_A710_2282622))
 
+# Process ERRATA_A710_2008768 flag
+$(eval $(call assert_boolean,ERRATA_A710_2008768))
+$(eval $(call add_define,ERRATA_A710_2008768))
+
 # Process ERRATA_N2_2067956 flag
 $(eval $(call assert_boolean,ERRATA_N2_2067956))
 $(eval $(call add_define,ERRATA_N2_2067956))