engines/libzbc: add libzbc_finish_zone() helper function

engines/libzbc: add libzbc_finish_zone() helper function

To support zone finish operation to ZBC drives through libzbc, add
finish_zone() callback to struct ioengine_ops, and implement in libzbc
IO engine. This feature is used to keep the same zone handling by
zonemode=zbd for libzbc engine as other engines.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Tested-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>