fru_area: cleanup headers

Cleanup headers, dropping sd-bus header and c-headers.  Add in cstdint
for uint8_t.

Change-Id: I751478a83ac807b688bb9b7d9efff2efc7578a4a
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/fru_area.hpp b/fru_area.hpp
index 6cebb3c..b725ddf 100644
--- a/fru_area.hpp
+++ b/fru_area.hpp
@@ -4,14 +4,13 @@
 #include "frup.hpp"
 #include "writefrudata.hpp"
 
-#include <stddef.h>
-#include <stdint.h>
-#include <systemd/sd-bus.h>
-
+#include <cstdint>
 #include <memory>
 #include <string>
 #include <vector>
 
+using std::uint8_t;
+
 class IPMIFruArea
 {
   private: