ide: use only ->set_pio_mode method for programming PIO modes (take 2)

Use ->set_pio_mode method to program PIO modes in ide_set_xfer_rate()
(the only place which used ->speedproc to program PIO modes) and remove
handling of PIO modes from all ->speedproc implementations.

v2:
* Fix pmac_ide_tune_chipset() comment.

There should be no functionality changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ppc/pmac.c b/drivers/ide/ppc/pmac.c
index 4da2518..f759a53 100644
--- a/drivers/ide/ppc/pmac.c
+++ b/drivers/ide/ppc/pmac.c
@@ -917,7 +917,7 @@
 
 /* 
  * Speedproc. This function is called by the core to set any of the standard
- * timing (PIO, MDMA or UDMA) to both the drive and the controller.
+ * DMA timing (MDMA or UDMA) to both the drive and the controller.
  * You may notice we don't use this function on normal "dma check" operation,
  * our dedicated function is more precise as it uses the drive provided
  * cycle time value. We should probably fix this one to deal with that too...
@@ -964,13 +964,6 @@
 		case XFER_SW_DMA_0:
 			return 1;
 #endif /* CONFIG_BLK_DEV_IDEDMA_PMAC */
-		case XFER_PIO_4:
-		case XFER_PIO_3:
-		case XFER_PIO_2:
-		case XFER_PIO_1:
-		case XFER_PIO_0:
-			pmac_ide_set_pio_mode(drive, speed & 0x07);
-			return 0;
 		default:
 			ret = 1;
 	}