fancontroller: Add missing config.h

Include config.h to satisfy #ifdef used in those files.

Change-Id: I0f6a3aa750abdf7b7c263d05f0551ee481b98d51
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
diff --git a/test/pid_fancontroller_unittest.cpp b/test/pid_fancontroller_unittest.cpp
index 8379113..6075a95 100644
--- a/test/pid_fancontroller_unittest.cpp
+++ b/test/pid_fancontroller_unittest.cpp
@@ -1,3 +1,5 @@
+#include "config.h"
+
 #include "pid/ec/logging.hpp"
 #include "pid/ec/pid.hpp"
 #include "pid/fancontroller.hpp"