net/mlx5e: kTLS, Fix TCP seq off-by-1 issue in TX resync flow

We have an off-by-1 issue in the TCP seq comparison.
The last sequence number that belongs to the TCP packet's payload
is not "start_seq + len", but one byte before it.
Fix it so the 'ends_before' is evaluated properly.

This fixes a bug that results in error completions in the
kTLS HW offload flows.

Fixes: ffbd9ca9

 ("net/mlx5e: kTLS, Fix corner-case checks in TX resync flow")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>