treewide: comply with the OpenBMC style guidelines

The guidelines say cpp source code filenames should be lower_snake_case:
https://github.com/openbmc/docs/blob/master/cpp-style-and-conventions.md#files

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: Ia04017b0eb9a65ce1303af5b6dc36e730410fd91
diff --git a/meson.build b/meson.build
index 5264985..aeb6445 100644
--- a/meson.build
+++ b/meson.build
@@ -203,8 +203,8 @@
         executable(
             'test_entity_manager',
             'test/test_entity-manager.cpp',
-            'src/Expression.cpp',
-            'src/Utils.cpp',
+            'src/expression.cpp',
+            'src/utils.cpp',
             cpp_args: test_boost_args,
             dependencies: [
                 boost,
@@ -223,7 +223,7 @@
         executable(
             'test_fru_utils',
             'test/test_fru-utils.cpp',
-            'src/FruUtils.cpp',
+            'src/fru_utils.cpp',
             cpp_args: test_boost_args,
             dependencies: [
                 boost,