Fix ATA SMART and CHECK POWER MODE

This patch fixes two things:

 1) CHECK POWER MODE

The error return value wasn't always zero, so it would show up as
offline.  Error is now explicitly set to zero.

 2) SMART

The smart values that were returned were invalid and tools like skdump
would not recognize that the smart data was actually valid and would
dump weird output.  The data has been fixed up and raw value support
was added.  Tools like skdump and palimpsest work as expected.

Signed-off-by: Brian Wheeler <bdwheele@indiana.edu>
Acked-by: Ryan Harper <ryanh@us.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
