ide: add ide_tune_dma() helper

After reworking the code responsible for selecting the best DMA
transfer mode it is now possible to add generic ide_tune_dma() helper.

Convert some IDE PCI host drivers to use it (the ones left need more work).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

diff --git a/drivers/ide/pci/triflex.c b/drivers/ide/pci/triflex.c
index 8a87723..35e8c61 100644
--- a/drivers/ide/pci/triflex.c
+++ b/drivers/ide/pci/triflex.c
@@ -100,20 +100,9 @@
 	(void) triflex_tune_chipset(drive, (XFER_PIO_0 + use_pio));
 }
 
-static int triflex_config_drive_for_dma(ide_drive_t *drive)
-{
-	u8 speed = ide_max_dma_mode(drive);
-
-	if (!speed)
-		return 0;
-
-	(void) triflex_tune_chipset(drive, speed);
-	 return ide_dma_enable(drive);
-}
-
 static int triflex_config_drive_xfer_rate(ide_drive_t *drive)
 {
-	if (ide_use_dma(drive) && triflex_config_drive_for_dma(drive))
+	if (ide_tune_dma(drive))
 		return 0;
 
 	triflex_tune_drive(drive, 255);