amd74xx: use ide_get_pair_dev() helper

There should be no functional changes caused by this patch.
Acked-by: NSergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/amd74xx.c

@@ -82,7 +82,7 @@ static void amd_set_drive(ide_drive_t *drive, const u8 speed)
 {
 	ide_hwif_t *hwif = drive->hwif;
 	struct pci_dev *dev = to_pci_dev(hwif->dev);
-	ide_drive_t *peer = hwif->drives + (~drive->dn & 1);
+	ide_drive_t *peer = ide_get_pair_dev(drive);
 	struct ide_timing t, p;
 	int T, UT;
 	u8 udma_mask = hwif->ultra_mask;
@@ -92,7 +92,7 @@ static void amd_set_drive(ide_drive_t *drive, const u8 speed)
 
 	ide_timing_compute(drive, speed, &t, T, UT);
 
-	if (peer->dev_flags & IDE_DFLAG_PRESENT) {
+	if (peer) {
 		ide_timing_compute(peer, peer->current_speed, &p, T, UT);
 		ide_timing_merge(&p, &t, &t, IDE_TIMING_8BIT);
 	}