writefrudata.cpp: add header for file

Add header writefrudata.hpp to corresponding file.

Change-Id: I2bec36d3c0744e7c496e7b7c161dfc6cf14bdf72
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/writefrudata.cpp b/writefrudata.cpp
index 6373416..181fa3c 100644
--- a/writefrudata.cpp
+++ b/writefrudata.cpp
@@ -1,3 +1,5 @@
+#include "writefrudata.hpp"
+
 #include "fru-area.hpp"
 #include "frup.hpp"
 #include "types.hpp"