ide: remove broken EXABYTENEST support

do_identify() marks EXABYTENEST device as non-present and frees
drive->id so enable_nest() has absolutely no chance of working.

The code was like this since at least 2.6.12-rc2 and nobody
has noticed so just remove broken EXABYTENEST support.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>