net/mlx5e: kTLS, Fix napi sync and possible use-after-free

Using synchronize_rcu() is sufficient to wait until running NAPI quits.

See similar upstream fix with detailed explanation:
("net/mlx5e: Use synchronize_rcu to sync with NAPI")

This change also fixes a possible use-after-free as the NAPI
might be already released at this stage.

Fixes: 0419d8c9 ("net/mlx5e: kTLS, Add kTLS RX resync support")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>