ide: add IDE_HFLAG_ABUSE_SET_DMA_MODE host flag

* Add IDE_HFLAG_ABUSE_SET_DMA_MODE host flag and use it to decide
  what to do with transfer modes < XFER_PIO_0 in ide_set_xfer_rate().

* Set IDE_HFLAG_ABUSE_SET_DMA_MODE in host drivers that need it
  (aec62xx, amd74xx, cs5520, cs5535, hpt34x, hpt366, pdc202xx_old,
  serverworks, tc86c001 and via82cxxx) and cleanup ->set_dma_mode
  methods in host drivers that don't (IDE core code guarantees that
  ->set_dma_mode will be called only for modes which are present
  in SWDMA/MWDMA/UDMA masks).

While at it:

* Add IDE_HFLAGS_HPT34X/HPT3XX/PDC202XX/SVWKS define in
  hpt34x/hpt366/pdc202xx_old/serverworks host driver.

There should be no functionality changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/scc_pata.c b/drivers/ide/pci/scc_pata.c
index ebb7132..24a85bb 100644
--- a/drivers/ide/pci/scc_pata.c
+++ b/drivers/ide/pci/scc_pata.c
@@ -254,19 +254,7 @@
 		offset = 0; /* 100MHz */
 	}
 
-	switch (speed) {
-	case XFER_UDMA_6:
-	case XFER_UDMA_5:
-	case XFER_UDMA_4:
-	case XFER_UDMA_3:
-	case XFER_UDMA_2:
-	case XFER_UDMA_1:
-	case XFER_UDMA_0:
-		idx = speed - XFER_UDMA_0;
-		break;
-	default:
-		return;
-	}
+	idx = speed - XFER_UDMA_0;
 
 	jcactsel = JCACTSELtbl[offset][idx];
 	if (is_slave) {