net/tls: simplify seq calculation in handle_device_resync()

We subtract "TLS_HEADER_SIZE - 1" from req_seq, then if they
match we add the same constant to seq.  Just add it to seq,
and we don't have to touch req_seq.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>