Don't disable PCI devices before changing the BARs, as discussed
recently.  Disabling PCI_COMMAND_MASTER bit is an obvious bug.

Further, pdev_enable_device() is a leftover from very old (2.0, I guess)
alpha PCI code.  It's used in pci_assign_unassigned_resources() to
enable *every* PCI device in the system.  So, if we have two graphic
cards on the same bus, both with legacy VGA IO...  oops.

Actually, only alpha relied on that due to the lack of
pcibios_enable_device (which has been already fixed).