block: Make BlockDriver method bdrv_eject() return void Callees always return 0, except for FreeBSD's cdrom_eject(), which returns -ENOTSUP when the device is in a terminally wedged state. The only caller is bdrv_eject(), and it maps -ENOTSUP to 0 since commit 4be9762a. Signed-off-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>