MFC: r287726

MFC: r287726

- Factor out the common and generic parts of the sparc64 host-PCI-bridge
  drivers into the revived sys/sparc64/pci/ofw_pci.c, previously already
  serving a similar purpose. This has been done with sun4v in mind, which
  explains a) the otherwise not that obvious scheme employed and b) why
  reusing sys/powerpc/ofw/ofw_pci.c was even lesser an option.
- Add a workaround for QEMU once again not emulating real machines, in
  this case by not providing the OFW_PCI_CS_MEM64 range. [1]

Submitted by:	jhb [1]

git-svn-id: svn://svn.freebsd.org/base/stable/10@292789 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f