ata: add/use ata_taskfile::{error|status} fields

[ Upstream commit efcef265fd83d9a68a68926abecb3e1dd3e260a8 ]

Add the explicit error and status register fields to 'struct ata_taskfile'
using the anonymous *union*s ('struct ide_taskfile' had that for ages!) and
update the libata taskfile code accordingly. There should be no object code
changes resulting from that...

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Stable-dep-of: 7390896b3484 ("ata: libata: fix NCQ autosense logic")
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/linux/libata.h

@@ -565,7 +565,10 @@ struct ata_taskfile {
 	u8			hob_lbam;
 	u8			hob_lbah;
 
-	u8			feature;
+	union {
+		u8		error;
+		u8		feature;
+	};
 	u8			nsect;
 	u8			lbal;
 	u8			lbam;
@@ -573,7 +576,10 @@ struct ata_taskfile {
 
 	u8			device;
 
-	u8			command;	/* IO operation */
+	union {
+		u8		status;
+		u8		command;
+	};
 
 	u32			auxiliary;	/* auxiliary field */
 						/* from SATA 3.1 and */