fuse: add file_modified() to fallocate

Add missing file_modified() call to fuse_file_fallocate().  Without this
fallocate on fuse failed to clear privileges.

Fixes: 05ba1f0823 ("fuse: add FALLOCATE operation")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/file.c

@@ -3001,6 +3001,10 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
 			goto out;
 	}
 
+	err = file_modified(file);
+	if (err)
+		goto out;
+
 	if (!(mode & FALLOC_FL_KEEP_SIZE))
 		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);