ide: add ->read_sff_dma_status method

Add ->read_sff_dma_status method for reading DMA Status register
and use it instead of ->INB.

While at it:

* Use inb() directly in ns87415.c::ns87415_dma_end().

There should be no functional changes caused by this patch.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/include/linux/ide.h b/include/linux/ide.h
index f58548b..ca0efbb 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -489,6 +489,8 @@
 	const struct ide_port_ops	*port_ops;
 	const struct ide_dma_ops	*dma_ops;
 
+	u8 (*read_sff_dma_status)(struct hwif_s *);
+
 	void (*tf_load)(ide_drive_t *, struct ide_task_s *);
 	void (*tf_read)(ide_drive_t *, struct ide_task_s *);