ide: remove ide_drive_t.usage

This field is no longer used by the core IDE code so fix ide-{disk,floppy}
drivers to keep openers count in the driver specific objects and remove
it from ide-{cd,scsi,tape} drivers (it was write-only).

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

6 files changed