After the panic teardown firmware command, health_care detects the error
in PCI bus and calls the mlx5_pci_err_detected. This health_care flow is
no longer needed because the panic teardown firmware command will bring
down the PCI bus communication with the HCA.

The solution is to cancel the health care timer and its pending
workqueue request before sending panic teardown firmware command.

Kernel trace:
mlx5_core 0033:01:00.0: Shutdown was called
mlx5_core 0033:01:00.0: health_care:154:(pid 9304): handling bad device here
mlx5_core 0033:01:00.0: mlx5_handle_bad_state:114:(pid 9304): NIC state 1
mlx5_core 0033:01:00.0: mlx5_pci_err_detected was called
mlx5_core 0033:01:00.0: mlx5_enter_error_state:96:(pid 9304): start
mlx5_3:mlx5_ib_event:3061:(pid 9304): warning: event on port 0
mlx5_core 0033:01:00.0: mlx5_enter_error_state:104:(pid 9304): end
Unable to handle kernel paging request for data at address 0x0000003f
Faulting instruction address: 0xc0080000434b8c80

Fixes: 8812c24d

 ('net/mlx5: Add fast unload support in shutdown flow')
Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>