adjust includes according to iwyu 3.5

fuse/operations.h

@@ -26,6 +26,12 @@
 #include "hashtbl.h"
 #include "../utils/stringv.h"
 
+struct fuse_conn_info;
+struct fuse_file_info;
+struct stat;
+struct statvfs;
+struct timespec;
+
 struct mediafirefs_context_private {
     mfconn         *conn;
     folder_tree    *tree;