PCI: hv: Fix synchronization between channel callback and hv_pci_bus_exit()

PCI: hv: Fix synchronization between channel callback and hv_pci_bus_exit()

[ Similarly to commit 00bfb885686ed ("PCI: hv: Fix synchronization
  between channel callback and hv_compose_msi_msg()"): ]

The (on-stack) teardown packet becomes invalid once the completion
timeout in hv_pci_bus_exit() has expired and hv_pci_bus_exit() has
returned.  Prevent the channel callback from accessing the invalid
packet by removing the ID associated to such packet from the VMbus
requestor in hv_pci_bus_exit().

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Link: https://lore.kernel.org/r/20220511223207.3386-3-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>