fix(cpus): workaround for Cortex-A720 erratum 2940794

Cortex-A720 erratum 2940794 is a Cat B erratum that is present
in revision r0p0, r0p1 and is fixed in r0p2.

The workaround is to set bit[37] of the CPUACTLR2_EL1 to 1.

SDEN documentation:
https://developer.arm.com/documentation/SDEN2439421/latest

Change-Id: I1488802e0ec7c16349c9633bb45de4d0e1faa9ad
Signed-off-by: Bipin Ravi <biprav01@u203721.austin.arm.com>
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 2164dac..b7e4236 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -936,6 +936,10 @@
 # only to revision r1p0. It is fixed in r1p1.
 CPU_FLAG_LIST += ERRATA_A715_2561034
 
+# Flag to apply erratum 2940794 workaround during reset. This erratum applies
+# to revisions r0p0 and r0p1. It is fixed in r0p2.
+CPU_FLAG_LIST += ERRATA_A720_2940794
+
 # Flag to apply DSU erratum 798953. This erratum applies to DSUs revision r0p0.
 # Applying the workaround results in higher DSU power consumption on idle.
 CPU_FLAG_LIST += ERRATA_DSU_798953