coda: use iterate_dir() in coda_readdir()

The code in coda_readdir() is nearly identical to iterate_dir().
Differences are:
 - iterate_dir() is killable
 - iterate_dir() adds permission checking and accessing notifications

I believe these are not harmful for coda so it is best to use
iterate_dir() directly.  This will allow locking changes without
touching the code in coda.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/20250608230952.20539-4-neil@brown.name
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/coda/dir.c

@@ -429,17 +429,9 @@ static int coda_readdir(struct file *coda_file, struct dir_context *ctx)
 	cfi = coda_ftoc(coda_file);
 	host_file = cfi->cfi_container;
 
-	if (host_file->f_op->iterate_shared) {
-		struct inode *host_inode = file_inode(host_file);
-		ret = -ENOENT;
-		if (!IS_DEADDIR(host_inode)) {
-			inode_lock_shared(host_inode);
-			ret = host_file->f_op->iterate_shared(host_file, ctx);
-			file_accessed(host_file);
-			inode_unlock_shared(host_inode);
-		}
+	ret = iterate_dir(host_file, ctx);
+	if (ret != -ENOTDIR)
 		return ret;
-	}
 	/* Venus: we must read Venus dirents from a file */
 	return coda_venus_readdir(coda_file, ctx);
 }