When kdump is triggered, some PCI devices may have not been shut down
cleanly before the kdump kernel starts.

This causes the initial attempt to enter D0 state in the kdump kernel to
fail with invalid device state returned from Hyper-V host.

When this happens, explicitly call hv_pci_bus_exit() and retry to enter
the D0 state.

Link: https://lore.kernel.org/r/20200507050300.10974-1-weh@microsoft.comSigned-off-by: Wei Hu <weh@microsoft.com>
[lorenzo.pieralisi@arm.com: commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>