net/mlx5: Fix memory leak when setting fpga ipsec caps

Allocated memory for context should be freed once
finished working with it.

Fixes: d6c4f029

 ("net/mlx5: Refactor accel IPSec code")
Signed-off-by: Talat Batheesh <talatb@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>