Utilizing all of the bring-up code in pci_enable and hba_enable,
this test issues a simple IDENTIFY command via the HBA and retrieves
the response via the PIO receive mechanisms of the HBA.

Bugs: The DPS interrupt (Descriptor Processed Status) does not
currently get set. This will need to be adjusted in a future
patch series when the AHCI DMA pathways are reworked to allow
the feature, which may be utilized by OSX guests.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1408643079-30675-9-git-send-email-jsnow@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>