DSU: Implement workaround for errata 798953

Under certain near idle conditions, DSU may miss response transfers on
the ACE master or Peripheral port, leading to deadlock. This workaround
disables high-level clock gating of the DSU to prevent this.

Change-Id: I820911d61570bacb38dd325b3519bc8d12caa14b
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/include/lib/cpus/aarch64/dsu_def.h b/include/lib/cpus/aarch64/dsu_def.h
index 4ec64ee..0969acf 100644
--- a/include/lib/cpus/aarch64/dsu_def.h
+++ b/include/lib/cpus/aarch64/dsu_def.h
@@ -31,6 +31,8 @@
  ********************************************************************/
 #define CLUSTERACTLR_EL1	S3_0_C15_C3_3
 
+#define CLUSTERACTLR_EL1_DISABLE_CLOCK_GATING	(ULL(1) << 15)
+
 /********************************************************************
  * Masks applied for DSU errata workarounds
  ********************************************************************/