block: floppy: fix rmmod lockup

Floppy rmmod locks up when no such hardware was initialized, since there is
nobody to wake the remove code up.  Remove the completion, because release is
called during platform_unregister anyway.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>