ide: remove broken disk byte-swapping support

Remove broken disk byte-swapping support:
- it can cause a data corruption on SMP (or if using PREEMPT on UP)
- all data coming from disk are byte-swapped by taskfile_*_data() which
  results in incorrect identify data being reported by /proc/ide/ and IOCTLs
- "hdx=bswap/byteswap" kernel parameter has been broken on m68k host drivers
  (including Atari/Q40 ones) since 2.5.x days (because of 'hwif' zero-ing)
- byte-swapping is limited to PIO transfers (for working with TiVo disks on
  x86 machines using user-space solutions or dm-byteswap should result in
  much better performance because DMA can be used)

For previous discussions please see:

http://www.ussg.iu.edu/hypermail/linux/kernel/0201.0/0768.html
http://lkml.org/lkml/2004/2/28/111

[ I have dm-byteswap device mapper target if somebody is interested
  (patch is for 2.6.4 though but I'll dust it off if needed). ]

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

include/linux/ide.h

@@ -394,7 +394,6 @@ typedef struct ide_drive_s {
 	u8	state;			/* retry state */
 	u8	waiting_for_dma;	/* dma currently in progress */
 	u8	unmask;			/* okay to unmask other irqs */
-	u8	bswap;			/* byte swap data */
 	u8	noflush;		/* don't attempt flushes */
 	u8	dsc_overlap;		/* DSC overlap */
 	u8	nice1;			/* give potential excess bandwidth */