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.
MFC: r260086

- Probe with BUS_PROBE_DEFAULT instead of 0.
- Remove clearing PCIM_CMD_INTxDIS; pci(4) will do that as appropriate since
  r189367.
MFC: r260058

- Remove a redundant variable in mpt_pci_attach().
- #if 0 the currently unused paired port linking and unlinking of dual
  adapters.
- Simplify MSI/MSI-X allocation and release. For a single one, we don't need
  to fiddle with the MSI/MSI-X count and pci_release_msi(9) is smart enough
  to just do nothing in case of INTx.
- Canonicalize actions taken on attach failure and detach.
- Remove the remainder of incomplete support for older FreeBSD versions.
MFC: r260061

- Add support for using MSI instead of INTx, controllable via the tunable
  hw.ral.msi_disable (defaulting to using MSI).
- Probe with BUS_PROBE_DEFAULT instead of 0.
- Nuke code setting PCI_POWERSTATE_D0; pci(4) already does that for type 0
  devices.
- Use PCIR_BAR instead of a homegrown macro.
- There's no need to keep track of resource IDs.
- Release resources again in case attaching fails.
- Quiesce the interrupt before detaching.
- Sprinkle const.
- Use DEVMETHOD_END.
- Use NULL instead of 0 for pointers.
- Trim headers.
- Nuke dupe $FreeBSD$.
MFC: r260063

- Probe with BUS_PROBE_DEFAULT instead of 0.
- Nuke code setting PCI_POWERSTATE_D0; pci(4) already does that for type 0
  devices.
- Use PCIR_BAR instead of a homegrown macro.
- There's no need to keep track of resource IDs.
- Quiesce the interrupt before actually detaching.
- Use DEVMETHOD_END.
- Use NULL instead of 0 for pointers.