MFC: r260053

MFC: r260053

- There's no need to keep track of resource IDs.
- Simplify MSI allocation and release. For a single one, we don't need to
  fiddle with the MSI count and pci_release_msi(9) is smart enough to just
  do nothing in case of INTx.
- Don't allocate MSI as RF_SHAREABLE.
- Use DEVMETHOD_END.
- Use NULL instead of 0 for pointers.

git-svn-id: svn://svn.freebsd.org/base/stable/10@264945 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f