staging: erofs: remove the redundant d_rehash() for the root dentry

There is actually no need at all to d_rehash() for the root dentry
as Al pointed out, fix it.
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/super.c

@@ -442,12 +442,6 @@ static int erofs_read_super(struct super_block *sb,
 
 	erofs_register_super(sb);
 
-	/*
-	 * We already have a positive dentry, which was instantiated
-	 * by d_make_root. Just need to d_rehash it.
-	 */
-	d_rehash(sb->s_root);
-
 	if (!silent)
 		infoln("mounted on %s with opts: %s.", dev_name,
 			(char *)data);