PCI: Remove unused SR-IOV VF Migration support

PCI: Remove unused SR-IOV VF Migration support

This reverts commit 74bb1bcc7dbb ("PCI: handle SR-IOV Virtual Function
Migration"), removing this exported interface:

  pci_sriov_migration()

Since pci_sriov_migration() is unused, it is impossible to schedule
sriov_migration_task() or use any of the other migration infrastructure.

This is based on Stephen Hemminger's patch (see link below), but goes a bit
further.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Bjorn Helgaas <[email protected]>
CC: Stephen Hemminger <[email protected]>