add needed include for numeric_limits

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I3dd819833048c1c5787814df064511913397ae78
diff --git a/pid/pidcontroller.hpp b/pid/pidcontroller.hpp
index 3d38c2a..0b491e7 100644
--- a/pid/pidcontroller.hpp
+++ b/pid/pidcontroller.hpp
@@ -4,6 +4,7 @@
 #include "ec/pid.hpp"
 #include "fan.hpp"
 
+#include <limits>
 #include <memory>
 #include <vector>