[libata] ahci: Add SATA GEN3 related messages

The present AHCI driver seems to support SATA GEN 3 speed, but the related
messages should be modified.

Signed-off-by: Shane Huang <shane.huang@amd.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/ahci.c

@@ -2446,6 +2446,8 @@ static void ahci_print_info(struct ata_host *host)
 		speed_s = "1.5";
 	else if (speed == 2)
 		speed_s = "3";
+	else if (speed == 3)
+		speed_s = "6";
 	else
 		speed_s = "?";