net: tls: export protocol version, cipher, tx_conf/rx_conf to socket diag

When an application configures kernel TLS on top of a TCP socket, it's
now possible for inet_diag_handler() to collect information regarding the
protocol version, the cipher type and TX / RX configuration, in case
INET_DIAG_INFO is requested.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>