ide: remove ->nice0 and ->nice2 fields from ide_drive_t

* ->nice0 and ->nice2 ide_drive_t fields are always zero so remove them.

* IDE_NICE_0 and IDE_NICE_2 defines from <linux/hdreg.h> are no longer
  used by any kernel code so cover them with #ifndef/#endif __KERNEL__.

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