set SATA spd according to spd limit
int sata_set_spd (
|struct ata_link * link|
Link to set SATA spd for
Set SATA spd of
link according to sata_spd_limit.
Inherited from caller.
0 if spd doesn't need to be changed, 1 if spd has been
changed. Negative errno if SCR registers are inaccessible.