Tegra: macro for legacy WDT FIQ handling

This patch adds the macro to enable legacy FIQ handling to the common
Tegra makefile. The default value of this macro is '0'. Platforms that
need this support should enable it from their makefiles.

This patch also helps fix violation of Rule 20.9.

Rule 20.9 "All identifiers used in the controlling expression of #if
           of #elif preprocessing directives shall be #define'd before
           evaluation"

Change-Id: I4f0c9917c044b5b1967fb5e79542cd3bf6e91f18
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

plat/nvidia/tegra/platform.mk

 #
 # Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2020, NVIDIA Corporation. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -37,9 +38,15 @@ WARMBOOT_ENABLE_DCACHE_EARLY := 1
 # remove the standard libc
 OVERRIDE_LIBC		:=	1
 
+# Flag to enable WDT FIQ interrupt handling for Tegra SoCs
+# prior to Tegra186
+ENABLE_WDT_LEGACY_FIQ_HANDLING	?= 0
+
 include plat/nvidia/tegra/common/tegra_common.mk
 include ${SOC_DIR}/platform_${TARGET_SOC}.mk
 
+$(eval $(call add_define,ENABLE_WDT_LEGACY_FIQ_HANDLING))
+
 # modify BUILD_PLAT to point to SoC specific build directory
 BUILD_PLAT	:=	${BUILD_BASE}/${PLAT}/${TARGET_SOC}/${BUILD_TYPE}