ide: add ->exec_command method

Add ->exec_command method for writing ATA Command register
and use it instead of ->OUTBSYNC.

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 a179a7f..d77c199 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -489,7 +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	(*exec_command)(struct hwif_s *, u8);
+	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 *);