TFTF: Add ARMv8.5 BTI support in makefiles

This patch adds 'BRANCH_PROTECTION' build option in
TFTF makefiles which corresponds to that in TF-A.
The option values are documented in 'build-options.rst'

Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Change-Id: Iad5083aee339cec574acf5e7ab1fd8142877a122
diff --git a/defaults.mk b/defaults.mk
index cf90aaf..ca44b47 100644
--- a/defaults.mk
+++ b/defaults.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2018-2019, Arm Limited. All rights reserved.
+# Copyright (c) 2018-2020, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -26,9 +26,6 @@
 # Build platform
 DEFAULT_PLAT		:= fvp
 
-# Enable Pointer Authentication support in the TFTF
-ENABLE_PAUTH		:= 0
-
 # Whether the Firmware Update images (i.e. NS_BL1U and NS_BL2U images) should be
 # built. The platform makefile is free to override this value.
 FIRMWARE_UPDATE		:= 0