dm io:ctl remove vmalloc void cast

In drivers/md/dm-ioctl.c::copy_params() there's a call to vmalloc()
where we currently cast the return value, but that's pretty pointless
given that vmalloc() returns "void *".
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-ioctl.c

@@ -1358,7 +1358,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl **param)
 	if (tmp.data_size < sizeof(tmp))
 		return -EINVAL;
 
-	dmi = (struct dm_ioctl *) vmalloc(tmp.data_size);
+	dmi = vmalloc(tmp.data_size);
 	if (!dmi)
 		return -ENOMEM;