kernel - Flesh out AHCI 1.3 regs / detection (FBSS not yet supported)

* Detect the CAP2 register.  Add definitions for new CAP and CAP2 bits.

* Detect and report FBSS support when a PM is attached.  Note that
  the driver does not yet support FBSS (I'm still tring to find a
  mobo whos AHCI has it).