Documentation: TLS: Add missing counter description

Add TLS TX counter description for the handshake retransmitted
packets that triggers the resync procedure then skip it, going
into the regular transmit flow.

Fixes: 46a3ea98 ("net/mlx5e: kTLS, Enhance TX resync flow")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>