ahci: trim signatures on raise/lower

ahci: trim signatures on raise/lower

These functions work on the AHCI device, not the individual
AHCI devices, so trim the AHCIDevice argument.

Signed-off-by: John Snow <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Reviewed-by: Jeff Cody <[email protected]>
Message-id: 20180531004323[email protected]
Signed-off-by: John Snow <[email protected]>