Use dev_printk() when possible so the IOMMU messages are more consistent
with other messages related to the device.

E.g., I think these messages related to surprise hotplug:

  pciehp 0000:80:10.0:pcie004: Slot(36): Link Down
  iommu: Removing device 0000:87:00.0 from group 12
  pciehp 0000:80:10.0:pcie004: Slot(36): Card present
  pcieport 0000:80:10.0: Data Link Layer Link Active not set in 1000 msec

would be easier to read as these (also requires some PCI changes not
included here):

  pci 0000:80:10.0: Slot(36): Link Down
  pci 0000:87:00.0: Removing from iommu group 12
  pci 0000:80:10.0: Slot(36): Card present
  pci 0000:80:10.0: Data Link Layer Link Active not set in 1000 msec
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>