mlx5: Return -EINVAL when WARN_ON_ONCE triggers in mlx5e_tls_resync().

Return value was changes to 'int' from void but this return statement
was not updated, or it slipped in via a merge.

Fixes: b5d9a834 ("net/tls: don't clear TX resync flag on error")
Signed-off-by: David S. Miller <davem@davemloft.net>