PCI: hv: Fix interrupt cleanup path

SR-IOV disabled from the host causes a memory leak.  pci-hyperv usually
first receives a PCI_EJECT notification and then proceeds to delete the
hpdev list entry in hv_eject_device_work().  Later in hv_msi_free() since
the device is no longer on the device list hpdev is NULL and hv_msi_free
returns without freeing int_desc as part of hv_int_desc_free().

Signed-off-by: Cathy Avery <cavery@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Jake Oshins <jakeo@microsoft.com>