selftests: tls: fix chacha+bidir tests

ChaCha support did not adjust the bidirectional test.
We need to set up KTLS in reverse direction correctly,
otherwise these two cases will fail:

  tls.12_chacha.bidir
  tls.13_chacha.bidir

Fixes: 4f336e88

 ("selftests/tls: add CHACHA20-POLY1305 to tls selftests")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Vadim Fedorenko <vfedorenko@novek.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>