net/mlx5_core: Add pci error handlers to mlx5_core driver

This patch implement the pci_error_handlers for mlx5_core which allow the
driver to recover from PCI error.

Once an error is detected in the PCI, the mlx5_pci_err_detected is called
and it:
1) Marks the device to be in 'Internal Error' state.
2) Dispatches an event to the mlx5_ib to flush all the outstanding cqes
with error.
3) Returns all the on going commands with error.
4) Unloads the driver.

Afterwards, the FW is reset and mlx5_pci_slot_reset is called and it
enables the device and restore it's pci state.

If the later succeeds, mlx5_pci_resume is called, and it loads the SW
stack.

Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>