floppy: remove duplicated code in redo_fd_request()

duplicated code in redo_fd_request(),
unlock_fdc() function has the same code "do_floppy = NULL" inside.

Signed-off-by: Yufeng Wang <wangyufeng@kylinos.cn>
Suggested-by: Denis Efremov <efremov@linux.com>
Link: https://lore.kernel.org/r/20240319014219.7812-1-wangyufeng@kylinos.cn


Signed-off-by: Jens Axboe <axboe@kernel.dk>