fsnotify/fdinfo: exportfs_encode_inode_fh() takes pointer as 4th argument

The call to exportfs_encode_inode_fh() takes an pointer
as the 4th argument, so replace the integer 0 with the
NULL pointer.

This fixes the following sparse warning:

fs/notify/fdinfo.c:53:87: warning: Using plain integer as NULL pointer

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ben Dooks <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/notify/fdinfo.c

···
 	f.handle.handle_bytes = sizeof(f.pad);
 	size = f.handle.handle_bytes >> 2;
 
-	ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, 0);
+	ret = exportfs_encode_inode_fh(inode, (struct fid *)f.handle.f_handle, &size, NULL);
 	if ((ret == FILEID_INVALID) || (ret < 0)) {
 		WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
 		return;