Tegra: macro for legacy WDT FIQ handling

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>