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/ide.c b/drivers/ide/ide.c
index c06424f..73f7521 100644
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -477,6 +477,7 @@
 
 	hwif->tuneproc			= tmp_hwif->tuneproc;
 	hwif->speedproc			= tmp_hwif->speedproc;
+	hwif->udma_filter		= tmp_hwif->udma_filter;
 	hwif->selectproc		= tmp_hwif->selectproc;
 	hwif->reset_poll		= tmp_hwif->reset_poll;
 	hwif->pre_reset			= tmp_hwif->pre_reset;