PCI/MSI: Disable MSI at enumeration even if kernel doesn't support MSI

If we enable MSI, then kexec a new kernel, the new kernel may receive MSIs
it is not prepared for.  Commit d5dea7d9

 ("PCI: msi: Disable msi
interrupts when we initialize a pci device") prevents this, but only if the
new kernel is built with CONFIG_PCI_MSI=y.

Move the "disable MSI" functionality from drivers/pci/msi.c to a new
pci_msi_setup_pci_dev() in drivers/pci/probe.c so we can disable MSIs when
we enumerate devices even if the kernel doesn't include full MSI support.

[bhelgaas: changelog, disable MSIs in pci_setup_device(), put
pci_msi_setup_pci_dev() at its final destination]
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>