[bazel] Fix constant exports

`BUILD` files should now be using `defs.bzl` for these, so we don't need
to export them from other files too.

Signed-off-by: James Wainwright <[email protected]>
(cherry picked from commit ea4702e)

Author: jwnrt

rules/opentitan/cc.bzl

@@ -2,13 +2,6 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
-load(
-    "@lowrisc_opentitan//rules:rv.bzl",
-    "rv_rule",
-    _OPENTITAN_CPU = "OPENTITAN_CPU",
-    _OPENTITAN_PLATFORM = "OPENTITAN_PLATFORM",
-    _opentitan_transition = "opentitan_transition",
-)
 load(
     "@lowrisc_opentitan//rules/opentitan:transform.bzl",
     "convert_to_vmem",
@@ -18,16 +11,11 @@ load(
 load("@lowrisc_opentitan//rules:signing.bzl", "sign_binary")
 load("@lowrisc_opentitan//rules/opentitan:exec_env.bzl", "ExecEnvInfo")
 load("@lowrisc_opentitan//rules/opentitan:util.bzl", "get_fallback", "get_override")
+load("@lowrisc_opentitan//rules:rv.bzl", "rv_rule")
 load("@rules_cc//cc:find_cc_toolchain.bzl", "find_cc_toolchain")
 load("//rules/opentitan:toolchain.bzl", "LOCALTOOLS_TOOLCHAIN")
 load("//rules/opentitan:util.bzl", "assemble_for_test")
 
-# Re-exports of names from transition.bzl; many files in the repo use opentitan.bzl
-# to get to them.
-OPENTITAN_CPU = _OPENTITAN_CPU
-OPENTITAN_PLATFORM = _OPENTITAN_PLATFORM
-opentitan_transition = _opentitan_transition
-
 def _expand(ctx, name, items):
     """Perform location and make_variable expansion on a list of items.
 

rules/opentitan/defs.bzl

@@ -66,8 +66,7 @@ load(
 # and opentitan_binary rules.
 CLEAR_KEY_SET = {"//signing:none_key": "none_key"}
 
-# Re-exports of names from transition.bzl; many files in the repo use opentitan.bzl
-# to get to them.
+# Re-exports of names from transition.bzl
 OPENTITAN_CPU = _OPENTITAN_CPU
 OPENTITAN_PLATFORM = _OPENTITAN_PLATFORM
 opentitan_transition = _opentitan_transition