selftests: mptcp: simult flows: fix some subtest names

commit 4d8e0dde upstream.

The selftest was correctly recording all the results, but the 'reverse
direction' part was missing in the name when needed.

It is important to have a unique (sub)test name in TAP, because some CI
environments drop tests with duplicated name.

Fixes: 675d9933 ("selftests: mptcp: simult flows: format subtests results in TAP")
Cc: stable@vger.kernel.org
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>