drivers/block/floppy.c: remove some unnecessary casting

Remove char/void __user * use.
Remove kmalloc cast.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>