ide: add struct ide_taskfile (take 2)

* Don't set write-only ide_task_t.hobRegister[6] and ide_task_t.hobRegister[7]
  in idedisk_set_max_address_ext().

* Add struct ide_taskfile and use it in ide_task_t instead of tfRegister[]
  and hobRegister[].

* Remove no longer needed IDE_CONTROL_OFFSET_HOB define.

* Add #ifndef/#endif __KERNEL__ around definitions of {task,hob}_struct_t.

While at it:

* Use ATA_LBA define for LBA bit (0x40) as suggested by Tejun Heo.

v2:
* Add missing newlines. (Noticed by Sergei)

* Use ~ATA_LBA instead of 0xBF. (Noticed by Sergei)

* Use unnamed unions for error/feature and status/command.
  (Suggested by Sergei).

There should be no functionality changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

include/linux/hdreg.h

@@ -117,7 +117,7 @@ typedef union ide_reg_valid_s {
 
 typedef struct ide_task_request_s {
 	__u8		io_ports[8];
-	__u8		hob_ports[8];
+	__u8		hob_ports[8]; /* bytes 6 and 7 are unused */
 	ide_reg_valid_t	out_flags;
 	ide_reg_valid_t	in_flags;
 	int		data_phase;
@@ -139,6 +139,7 @@ struct hd_drive_cmd_hdr {
 	__u8 sector_count;
 };
 
+#ifndef __KERNEL__
 typedef struct hd_drive_task_hdr {
 	__u8 data;
 	__u8 feature;
@@ -160,6 +161,7 @@ typedef struct hd_drive_hob_hdr {
 	__u8 device_head;
 	__u8 control;
 } hob_struct_t;
+#endif
 
 #define TASKFILE_INVALID		0x7fff
 #define TASKFILE_48			0x8000