PCI: hv: Handle hv_pci_generic_compl() error case

'completion_status' is used in some places, e.g.,
hv_pci_protocol_negotiation(), so we should make sure it's initialized in
error case too, though the error is unlikely here.

[bhelgaas: fix changelog typo and nearby whitespace]
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: KY Srinivasan <kys@microsoft.com>
CC: Jake Oshins <jakeo@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Vitaly Kuznetsov <vkuznets@redhat.com>