sata_highbank: use ATA_BUSY

ahci_highbank_hardreset() uses bare number for the BSY bit of the ATA status
register, despite it is #define'd in <linux/ata.h>

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>