fix(tc): enable the execution of both platform tests

fix(tc): enable the execution of both platform tests

The C preprocessor cannot compare defines against strings.
Such an expression is always evaluated to be true. Therefore,
its usage in a conditional expression results that always the
first branch is taken. Other branches cannot be reached by
any configuration value. The fix removes this string comparison
and instead it introduces distinct defines for all the cases.

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: Ia1142b31b6778686c74e1e882fe4604fe3b6501d