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/slc90e66.c b/drivers/ide/pci/slc90e66.c
index eb4445b..dbbb468 100644
--- a/drivers/ide/pci/slc90e66.c
+++ b/drivers/ide/pci/slc90e66.c
@@ -91,19 +91,9 @@
 	pci_read_config_word(dev, 0x48, &reg48);
 	pci_read_config_word(dev, 0x4a, &reg4a);
 
-	switch(speed) {
-		case XFER_UDMA_4:	u_speed = 4 << (drive->dn * 4); break;
-		case XFER_UDMA_3:	u_speed = 3 << (drive->dn * 4); break;
-		case XFER_UDMA_2:	u_speed = 2 << (drive->dn * 4); break;
-		case XFER_UDMA_1:	u_speed = 1 << (drive->dn * 4); break;
-		case XFER_UDMA_0:	u_speed = 0 << (drive->dn * 4); break;
-		case XFER_MW_DMA_2:
-		case XFER_MW_DMA_1:
-		case XFER_SW_DMA_2:	break;
-		default:		return;
-	}
-
 	if (speed >= XFER_UDMA_0) {
+		u_speed = (speed - XFER_UDMA_0) << (drive->dn * 4);
+
 		if (!(reg48 & u_flag))
 			pci_write_config_word(dev, 0x48, reg48|u_flag);
 		/* FIXME: (reg4a & a_speed) ? */