fix verilator git steps

If following the git steps in the main README to clone repo, it requires
adding submodule path to make the git submodule update command,
given in the verilator README, works.

hw/verilated/README.md

@@ -21,7 +21,7 @@ sudo make install
 ## Rust integration tests:
 
 ```shell
-git submodule update --init"  # Needed the first time
+git submodule update --init hw/1.0/rtl/"  # Needed the first time
 (cd hw/verilated && cargo test --features verilator)
 (cd hw-model && cargo test --features verilator)
 ```