MFC 480570dbb309:
Fixes for SRIOV in mlx5core.

• call pci_iov_detach() on detaching from PCI device to take care of hang on destroying VFs after PF is down.

• disable eswitch SRIOV support right after pci_iov_detach(), else the eswitch cleanup sometimes occur while the SRIOV flow table is still present.

Sponsored by: Mellanox Technologies // NVIDIA Networking