ide: remove unused XFER_UDMA_SLOW

Remove unused XFER_UDMA_SLOW from ide_timing[].

While at it:

- fix re-defining XFER_PIO_5 (no need to define it in ide-timing.h as
  it is defined in <linux/ata.h> which is included by <linux/hdreg.h>)

- fix whitespace damage

There should be no functional changes caused by this patch.

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