AHCI/SILI - Send dummy SETXFER mode even though it is SATA
* If the identify structure contains a non-zero/non-FFFF dmamode field
we send a dummy SETXFER mode command to the device.
* Most SATA DISK devices set this field to 0 or FFFF and in this case no
SETXFER mode command is sent. SETXFER is non-applicable to SATA in
general.
Most ATAPI devices still initialize the dmamode field and some ATAPI
devices still require SETXFER to be sent even though they are native SATA.
SATA->PATA converters may require a SETXFER to be passed through before
the PATA devices will operate properly. In this case the dmamode field
will likely be initialized.