fs: ufs: remove cast for kmalloc return value

remove cast for kmalloc return value.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>