net/mlx5: Add missing mutex destroy

Add mutex destroy calls to balance with mutex_init() done in the init
path.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>