ide: rework the code for selecting the best DMA transfer mode (v3)

Depends on the "ide: fix UDMA/MWDMA/SWDMA masks" patch.

* add ide_hwif_t.udma_filter hook for filtering UDMA mask
  (use it in alim15x3, hpt366, siimage and serverworks drivers)
* add ide_max_dma_mode() for finding best DMA mode for the device
  (loosely based on some older libata-core.c code)
* convert ide_dma_speed() users to use ide_max_dma_mode()
* make ide_rate_filter() take "ide_drive_t *drive" as an argument instead
  of "u8 mode" and teach it to how to use UDMA mask to do filtering
* use ide_rate_filter() in hpt366 driver
* remove no longer needed ide_dma_speed() and *_ratemask()
* unexport eighty_ninty_three()

v2:
* rename ->filter_udma_mask to ->udma_filter
  [ Suggested by Sergei Shtylyov <sshtylyov@ru.mvista.com>. ]

v3:
* updated for scc_pata driver (fixes XFER_UDMA_6 filtering for user-space
  originated transfer mode change requests when 100MHz clock is used)

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/pci/slc90e66.c b/drivers/ide/pci/slc90e66.c
index 852ccb3..9e95a5c 100644
--- a/drivers/ide/pci/slc90e66.c
+++ b/drivers/ide/pci/slc90e66.c
@@ -21,15 +21,6 @@
 
 #include <asm/io.h>
 
-static u8 slc90e66_ratemask (ide_drive_t *drive)
-{
-	u8 mode	= 2;
-
-	if (!eighty_ninty_three(drive))
-		mode = min_t(u8, mode, 1);
-	return mode;
-}
-
 static u8 slc90e66_dma_2_pio (u8 xfer_rate) {
 	switch(xfer_rate) {
 		case XFER_UDMA_4:
@@ -122,7 +113,7 @@
 	ide_hwif_t *hwif	= HWIF(drive);
 	struct pci_dev *dev	= hwif->pci_dev;
 	u8 maslave		= hwif->channel ? 0x42 : 0x40;
-	u8 speed	= ide_rate_filter(slc90e66_ratemask(drive), xferspeed);
+	u8 speed		= ide_rate_filter(drive, xferspeed);
 	int sitre = 0, a_speed	= 7 << (drive->dn * 4);
 	int u_speed = 0, u_flag = 1 << drive->dn;
 	u16			reg4042, reg44, reg48, reg4a;
@@ -171,7 +162,7 @@
 
 static int slc90e66_config_drive_for_dma (ide_drive_t *drive)
 {
-	u8 speed = ide_dma_speed(drive, slc90e66_ratemask(drive));
+	u8 speed = ide_max_dma_mode(drive);
 
 	if (!speed)
 		return 0;