use_clustering (sht) bit set to 0 in AHCI ?

ahci: enable sg segment clustering

The specification states that ahci supports segments up to 4MiB in size,
so enable clustering.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/ata/ahci.c

@@ -54,7 +54,7 @@ enum {
 	AHCI_MAX_PORTS		= 32,
 	AHCI_MAX_SG		= 168, /* hardware max is 64K */
 	AHCI_DMA_BOUNDARY	= 0xffffffff,
-	AHCI_USE_CLUSTERING	= 0,
+	AHCI_USE_CLUSTERING	= 1,
 	AHCI_MAX_CMDS		= 32,
 	AHCI_CMD_SZ		= 32,
 	AHCI_CMD_SLOT_SZ	= AHCI_MAX_CMDS * AHCI_CMD_SZ,