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>
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index d6e6748..f77a673 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -3684,7 +3684,7 @@
 	ata_reset_fn_t hardreset = ops->hardreset;
 
 	/* ignore built-in hardreset if SCR access is not available */
-	if (ata_is_builtin_hardreset(hardreset) && !sata_scr_valid(&ap->link))
+	if (hardreset == sata_std_hardreset && !sata_scr_valid(&ap->link))
 		hardreset = NULL;
 
 	ata_do_eh(ap, ops->prereset, ops->softreset, hardreset, ops->postreset);