PCI: vmd: Reset VMD config register between soft reboots

VMD driver can disable or enable MSI remapping by changing
VMCONFIG_MSI_REMAP register. This register needs to be set to the
default value during soft reboots. Drives failed to enumerate
when Windows boots after performing a soft reboot from Linux.
Windows doesn't support MSI remapping disable feature and stale
register value hinders Windows VMD driver initialization process.
Adding vmd_shutdown function to make sure to set the VMCONFIG
register to the default value.

Link: https://lore.kernel.org/r/20230224202811.644370-1-nirmal.patel@linux.intel.com


Fixes: ee81ee84 ("PCI: vmd: Disable MSI-X remapping when possible")
Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Jon Derrick <jonathan.derrick@linux.dev>