PCI: hv: Fix wslot_to_devfn() to fix warnings on device removal

The devfn of 00:02.0 is 0x10.  devfn_to_wslot(0x10) == 0x2, and
wslot_to_devfn(0x2) should be 0x10, while it's 0x2 in the current code.

Due to this, hv_eject_device_work() -> pci_get_domain_bus_and_slot()
returns NULL and pci_stop_and_remove_bus_device() is not called.

Later when the real device driver's .remove() is invoked by
hv_pci_remove() -> pci_stop_root_bus(), some warnings can be noticed
because the VM has lost the access to the underlying device at that
time.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Haiyang Zhang <haiyangz@microsoft.com>
CC: stable@vger.kernel.org
CC: K. Y. Srinivasan <kys@microsoft.com>
CC: Stephen Hemminger <sthemmin@microsoft.com>