drm/vmwgfx: Fix an issue with the device losing its irq line on module unload

Starting with commit b4b55cda
("x86/PCI: Refine the way to release PCI IRQ resources")

the device lost its irq resource on module unload. While that's ok and
apparently intentional, the driver never got the resource back on module load

The code apparently wants drivers to disable the pci device at pci device
driver removal, so lets do that. That fixes the issue.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>