kernel - More AHCI work to help support broken AMD chipsets

kernel - More AHCI work to help support broken AMD chipsets

This cleans up more of our AHCI support for AMD 880/890/SB850 chipsets.

This does NOT clean up hot-plug issues (fixing those might require actually
probing dead ports every few seconds).

* Better PCS/PRCS masking during low level reset sequences to prevent
  the PCS/PRCS interrupt from poking ports while we are in a hard reset.

* Breakout the COMRESET sequence into its own procedure.

* Make sure SPM is disabled in addition to IPM when doing a hard reset
  of a port.  Also make sure that POD (Power Up Device) is set in
  addition to SUD (Spin up Device) while we are in a hard reset.

* Wait one full second after aftering DET_INIT (sending COMINIT) before
  testing the SSTS bits, to ensure the microcontroller has reinitialized
  itself so we do not get bogus bits and to prevent bogus device detection
  which some chipsets may have left unmasked.

  This may also be needed in general when supporting SATA-III's longer
  training times.

* Do not reinit the port after a PM probe fails as it could undo all of
  the hard work we did initializing it.

* Reissue the COMRESET if a PM probe fails to ensure that any state left
  over from the PM detection gets cleared and to deal with any devices
  which brick when they receive a PM-related command.