libata: unify mechanism to request follow-up SRST

Previously, there were two ways to trigger follow-up SRST from
hardreset method - returning -EAGAIN and leaving all device classes
unmodified.  Drivers never used the latter mechanism and the only use
case for the former was when hardreset couldn't classify.

Drop the latter mechanism and let -EAGAIN mean "perform follow-up SRST
if classification is required".  This change removes unnecessary
follow-up SRSTs and simplifies reset implementations.

Signed-off-by: Tejun Heo <htejun@gmail.com>
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index d8c4a45..4ec1397 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2055,20 +2055,10 @@
 	if (rc)
 		return rc;
 
-	/* If any class isn't ATA_DEV_UNKNOWN, consider classification
-	 * is complete and convert all ATA_DEV_UNKNOWN to
-	 * ATA_DEV_NONE.
-	 */
+	/* convert all ATA_DEV_UNKNOWN to ATA_DEV_NONE */
 	ata_link_for_each_dev(dev, link)
-		if (classes[dev->devno] != ATA_DEV_UNKNOWN)
-			break;
-
-	if (dev) {
-		ata_link_for_each_dev(dev, link) {
-			if (classes[dev->devno] == ATA_DEV_UNKNOWN)
-				classes[dev->devno] = ATA_DEV_NONE;
-		}
-	}
+		if (classes[dev->devno] == ATA_DEV_UNKNOWN)
+			classes[dev->devno] = ATA_DEV_NONE;
 
 	return 0;
 }
@@ -2079,15 +2069,15 @@
 {
 	if (link->flags & ATA_LFLAG_NO_SRST)
 		return 0;
-	if (rc == -EAGAIN)
-		return 1;
+	if (rc == -EAGAIN) {
+		if (classify)
+			return 1;
+		rc = 0;
+	}
 	if (rc != 0)
 		return 0;
 	if ((link->ap->flags & ATA_FLAG_PMP) && ata_is_host_link(link))
 		return 1;
-	if (classify && !(link->flags & ATA_LFLAG_ASSUME_CLASS) &&
-	    classes[0] == ATA_DEV_UNKNOWN)
-		return 1;
 	return 0;
 }