ide: always disable DMA before tuning it

ide_start_power_step() and set_using_dma() were missing ->dma_off_quietly
call (comment in probe_hwif() states that DMA should be always cleared before
tuning is attempted).  Fix it.
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-io.c

@@ -223,6 +223,7 @@ static ide_startstop_t ide_start_power_step(ide_drive_t *drive, struct request *
 			break;
 		if (drive->hwif->ide_dma_check == NULL)
 			break;
+		drive->hwif->dma_off_quietly(drive);
 		ide_set_dma(drive);
 		break;
 	}

drivers/ide/ide.c

@@ -910,6 +910,7 @@ int set_using_dma(ide_drive_t *drive, int arg)
 	err = 0;
 
 	if (arg) {
+		hwif->dma_off_quietly(drive);
 		if (ide_set_dma(drive) || hwif->ide_dma_on(drive))
 			err = -EIO;
 	} else