add_gendisk()/del_gendisk() moved into ->reinit() and ->cleanup() of
ide-{disk,cd,floppy} - i.e.  moments when high-levle driver claims/gives
up a drive.

register_disk() also shifted into ->reinit().

consequently, revalidate_drives() is gone (it did messy postponed
rereading of partition tables; not needed anymore).  Ditto for
ide_geninit().

regular 2.5 changes in ->revalidate() and BLKRRPART handling - same as
all other block devices.