meson: switch config.h to config.hpp

Enable a transition of this file from C to C++ so that we
can use C++ constants instead of #defines in future commits.

Change-Id: I1149ebdaaeb99b7e7974ca846b9b07a3399edea0
Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/src/button_handler.cpp b/src/button_handler.cpp
old mode 100755
new mode 100644
index 2d1f1eb..ae9cc5d
--- a/src/button_handler.cpp
+++ b/src/button_handler.cpp
@@ -1,7 +1,6 @@
-#include "config.h"
-
 #include "button_handler.hpp"
 
+#include "config.hpp"
 #include "power_button_profile_factory.hpp"
 
 #include <phosphor-logging/lg2.hpp>