nbd: Remove superfluous casts

In Linux kernel code it is preferred not to use a cast when converting a
void pointer to another pointer type.

Cc: Christoph Hellwig <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: Yu Kuai <[email protected]>
Cc: Markus Pargmann <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: bvanassche

drivers/block/nbd.c

@@ -222,7 +222,7 @@ static ssize_t pid_show(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {
 	struct gendisk *disk = dev_to_disk(dev);
-	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
+	struct nbd_device *nbd = disk->private_data;
 
 	return sprintf(buf, "%d\n", nbd->pid);
 }
@@ -236,7 +236,7 @@ static ssize_t backend_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
 	struct gendisk *disk = dev_to_disk(dev);
-	struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
+	struct nbd_device *nbd = disk->private_data;
 
 	return sprintf(buf, "%s\n", nbd->backend ?: "");
 }