btrfs: remove unused parameters from btrfs_cmp_data

After the page locking has been reworked, we get all pages prepared via
cmp_pages.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3053,8 +3053,7 @@ out:
 	return 0;
 }
 
-static int btrfs_cmp_data(struct inode *src, u64 loff, struct inode *dst,
-			  u64 dst_loff, u64 len, struct cmp_pages *cmp)
+static int btrfs_cmp_data(u64 len, struct cmp_pages *cmp)
 {
 	int ret = 0;
 	int i;
@@ -3221,7 +3220,7 @@ again:
 	}
 
 	/* pass original length for comparison so we stay within i_size */
-	ret = btrfs_cmp_data(src, loff, dst, dst_loff, olen, &cmp);
+	ret = btrfs_cmp_data(olen, &cmp);
 	if (ret == 0)
 		ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);