TFTF: Add ARMv8.5 BTI-related definitions

This patch adds BTI-related definitions in header files
which fully correspond to those in TF-A source tree.

Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Change-Id: I1ae4c13dab41b0099517dd1bead221909511f2fc
diff --git a/include/lib/xlat_tables/xlat_tables_defs.h b/include/lib/xlat_tables/xlat_tables_defs.h
index 8a5ce53..1fd3c83 100644
--- a/include/lib/xlat_tables/xlat_tables_defs.h
+++ b/include/lib/xlat_tables/xlat_tables_defs.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -62,6 +62,11 @@
 #define OSH			(U(0x2) << 6)
 #define ISH			(U(0x3) << 6)
 
+#ifdef __aarch64__
+/* Guarded Page bit */
+#define GP			(ULL(1) << 50)
+#endif
+
 #define TABLE_ADDR_MASK		ULL(0x0000FFFFFFFFF000)
 
 /*