MFC: r233403, r233404

MFC: r233403, r233404

- Use the PCI ID macros from mpi_cnfg.h rather than duplicating them here.
  Note that this driver additionally probes some device IDs for the most
  part not know to other MPT drivers, if at all. So rename the macros not
  present in mpi_cnfg.h to match the naming scheme in the latter and but
  suffix them with a _FB in order to not cause conflicts.
- Like mpt_set_config_regs(), comment out mpt_read_config_regs() as the
  content of the registers read isn't actually used and both functions
  aren't exactly up to date regarding the possible layouts of the BARs
  (these function might be helpful for debugging though, so don't remove
  them completely).
- Use DEVMETHOD_END.
- Use NULL rather than 0 for pointers.
- Remove an unusual check for the softc being NULL.
- Remove redundant zeroing of the softc.
- Remove an overly banal and actually partly incorrect as well as partly
  outdated comment regarding the allocation of the memory resource.

git-svn-id: svn://svn.freebsd.org/base/stable/9@233721 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f