md: get_disk_info(): Don't convert between signed and unsigned and back.

The current code copies a signed int from user space, converts it to
unsigned and passes the unsigned value to find_rdev_nr() which expects
a signed value. Simply pass the signed value from user space directly.
Signed-off-by: Andre Noll <maan@systemlinux.org>
Signed-off-by: Neil Brown <neilb@suse.de>

drivers/md/md.c

@@ -4186,15 +4186,12 @@ static int get_bitmap_file(mddev_t * mddev, void __user * arg)
 static int get_disk_info(mddev_t * mddev, void __user * arg)
 {
 	mdu_disk_info_t info;
-	unsigned int nr;
 	mdk_rdev_t *rdev;
 
 	if (copy_from_user(&info, arg, sizeof(info)))
 		return -EFAULT;
 
-	nr = info.number;
-
-	rdev = find_rdev_nr(mddev, nr);
+	rdev = find_rdev_nr(mddev, info.number);
 	if (rdev) {
 		info.major = MAJOR(rdev->bdev->bd_dev);
 		info.minor = MINOR(rdev->bdev->bd_dev);