libata-sff: separate out BMDMA EH

Some of error handling logic in ata_sff_error_handler() and all of
ata_sff_post_internal_cmd() are for BMDMA.  Create
ata_bmdma_error_handler() and ata_bmdma_post_internal_cmd() and move
BMDMA part into those.

While at it, change DMA protocol check to ata_is_dma(), fix
post_internal_cmd to call ap->ops->bmdma_stop instead of directly
calling ata_bmdma_stop() and open code hardreset selection so that
ata_std_error_handler() doesn't have to know about sff hardreset.

As these two functions are BMDMA specific, there's no reason to check
for bmdma_addr before calling bmdma methods if the protocol of the
failed command is DMA.  sata_mv and pata_mpc52xx now don't need to set
.post_internal_cmd to ATA_OP_NULL and pata_icside and sata_qstor don't
need to set it to their bmdma_stop routines.

ata_sff_post_internal_cmd() becomes noop and is removed.

This fixes p3 described in clean-up-BMDMA-initialization patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_qstor.c

@@ -147,7 +147,6 @@ static struct ata_port_operations qs_ata_ops = {
 	.prereset		= qs_prereset,
 	.softreset		= ATA_OP_NULL,
 	.error_handler		= qs_error_handler,
-	.post_internal_cmd	= ATA_OP_NULL,
 	.lost_interrupt		= ATA_OP_NULL,
 
 	.scr_read		= qs_scr_read,
@@ -255,7 +254,7 @@ static int qs_scr_read(struct ata_link *link, unsigned int sc_reg, u32 *val)
 static void qs_error_handler(struct ata_port *ap)
 {
 	qs_enter_reg_mode(ap);
-	ata_std_error_handler(ap);
+	ata_sff_error_handler(ap);
 }
 
 static int qs_scr_write(struct ata_link *link, unsigned int sc_reg, u32 val)