libata: clean up xfermode / PATA timing related stuff

* s/ATA_BITS_(PIO|MWDMA|UDMA)/ATA_NR_\1_MODES/g

* Consistently use 0xff to indicate invalid transfer mode (0x00 is
  valid for PIO_SLOW).

* Make ata_xfer_mode2mask() return proper mode mask instead of just
  the highest bit.

* Sort ata_timing table in increasing xfermode order and update
  ata_timing_find_mode() accordingly.

This patch doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 083dd77..e2ed3ba 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -269,17 +269,20 @@
 	/* encoding various smaller bitmaps into a single
 	 * unsigned int bitmap
 	 */
-	ATA_BITS_PIO		= 7,
-	ATA_BITS_MWDMA		= 5,
-	ATA_BITS_UDMA		= 8,
+	ATA_NR_PIO_MODES	= 7,
+	ATA_NR_MWDMA_MODES	= 5,
+	ATA_NR_UDMA_MODES	= 8,
 
 	ATA_SHIFT_PIO		= 0,
-	ATA_SHIFT_MWDMA		= ATA_SHIFT_PIO + ATA_BITS_PIO,
-	ATA_SHIFT_UDMA		= ATA_SHIFT_MWDMA + ATA_BITS_MWDMA,
+	ATA_SHIFT_MWDMA		= ATA_SHIFT_PIO + ATA_NR_PIO_MODES,
+	ATA_SHIFT_UDMA		= ATA_SHIFT_MWDMA + ATA_NR_MWDMA_MODES,
 
-	ATA_MASK_PIO		= ((1 << ATA_BITS_PIO) - 1) << ATA_SHIFT_PIO,
-	ATA_MASK_MWDMA		= ((1 << ATA_BITS_MWDMA) - 1) << ATA_SHIFT_MWDMA,
-	ATA_MASK_UDMA		= ((1 << ATA_BITS_UDMA) - 1) << ATA_SHIFT_UDMA,
+	ATA_MASK_PIO		= ((1 << ATA_NR_PIO_MODES) - 1)
+					<< ATA_SHIFT_PIO,
+	ATA_MASK_MWDMA		= ((1 << ATA_NR_MWDMA_MODES) - 1)
+					<< ATA_SHIFT_MWDMA,
+	ATA_MASK_UDMA		= ((1 << ATA_NR_UDMA_MODES) - 1)
+					<< ATA_SHIFT_UDMA,
 
 	/* size of buffer to pad xfers ending on unaligned boundaries */
 	ATA_DMA_PAD_SZ		= 4,