libata: implement and use sata_std_hardreset()

Implement sata_std_hardreset(), which simply wraps around
sata_link_hardreset().  sata_std_hardreset() becomes new standard
hardreset method for sata_port_ops and sata_sff_hardreset() moves from
ata_base_port_ops to ata_sff_port_ops, which is where it really
belongs.

ata_is_builtin_hardreset() is added so that both
ata_std_error_handler() and ata_sff_error_handler() skip both builtin
hardresets if SCR isn't accessible.

piix_sidpr_hardreset() in ata_piix.c is identical to
sata_std_hardreset() in functionality and got replaced with the
standard function.

Signed-off-by: Tejun Heo <htejun@gmail.com>
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index f4f9c27..21687bb 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2857,11 +2857,8 @@
 	struct ata_port_operations *ops = ap->ops;
 	ata_reset_fn_t hardreset = ops->hardreset;
 
-	/* sata_std_hardreset is inherited to all drivers from
-	 * ata_base_port_ops.  Ignore it if SCR access is not
-	 * available.
-	 */
-	if (hardreset == sata_sff_hardreset && !sata_scr_valid(&ap->link))
+	/* ignore built-in hardreset if SCR access is not available */
+	if (ata_is_builtin_hardreset(hardreset) && !sata_scr_valid(&ap->link))
 		hardreset = NULL;
 
 	ata_do_eh(ap, ops->prereset, ops->softreset, hardreset, ops->postreset);