Move variant usage to std

Since sdbusplus now uses std, it's cleaner just to
use the variant type directly not behind the namespace.

Also updates clang format.

Style only change.

Tested-by: It builds

Change-Id: I2b7e3ae6b0135cda3e8443e8f910009e6e857f87
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/include/Overlay.hpp b/include/Overlay.hpp
index 54a8964..d3c8eff 100644
--- a/include/Overlay.hpp
+++ b/include/Overlay.hpp
@@ -18,4 +18,4 @@
 #include <nlohmann/json.hpp>
 
 void unloadAllOverlays(void);
-bool loadOverlays(const nlohmann::json &systemConfiguration);
\ No newline at end of file
+bool loadOverlays(const nlohmann::json& systemConfiguration);
\ No newline at end of file