libata: implement ata_timing_cycle2mode() and use it in libata-acpi and pata_acpi

libata-acpi is using separate timing tables for transfer modes
although libata-core has the complete ata_timing table.  Implement
ata_timing_cycle2mode() to look for matching mode given transfer type
and cycle duration and use it in libata-acpi and pata_acpi to replace
private timing tables.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 8022e5b..8ede93b 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -941,6 +941,7 @@
 extern void ata_timing_merge(const struct ata_timing *,
 			     const struct ata_timing *, struct ata_timing *,
 			     unsigned int);
+extern u8 ata_timing_cycle2mode(unsigned int xfer_shift, int cycle);
 
 enum {
 	ATA_TIMING_SETUP	= (1 << 0),
@@ -961,10 +962,6 @@
 
 /* libata-acpi.c */
 #ifdef CONFIG_ATA_ACPI
-extern const unsigned int ata_acpi_pio_cycle[7];
-extern const unsigned int ata_acpi_mwdma_cycle[5];
-extern const unsigned int ata_acpi_udma_cycle[7];
-
 static inline const struct ata_acpi_gtm *ata_acpi_init_gtm(struct ata_port *ap)
 {
 	if (ap->pflags & ATA_PFLAG_INIT_GTM_VALID)