[top_earlgrey] Fix usage of legacy rules

Signed-off-by: Amaury Pouly <[email protected]>

hw/top_earlgrey/sw/cw310/BUILD

@@ -2,7 +2,7 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
-load("//rules:opentitan.bzl", "OPENTITAN_CPU")
+load("//rules/opentitan:defs.bzl", "OPENTITAN_CPU")
 
 package(default_visibility = ["//visibility:public"])