libata: add @spd_limit to sata_down_spd_limit()

Add @spd_limit to sata_down_spd_limit() so that the caller can specify
the SPD limit it wants.  This parameter doesn't get in the way even
when it's too low.  The closest possible limit is applied.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 98ca07a..619f2c3 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -729,7 +729,7 @@
 		if (tries) {
 			/* consecutive revalidation failures? speed down */
 			if (reval_failed)
-				sata_down_spd_limit(link);
+				sata_down_spd_limit(link, 0);
 			else
 				reval_failed = 1;