net/mlx5: Cancel recovery work in remove flow

If there is pending delayed work for health recovery it must be canceled
if the device is being unloaded.

Fixes: 05ac2c0b

 ("net/mlx5: Fix race between PCI error handlers and health work")
Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>