Include missing header file

we are using the std algo's in this file
but missed to include the c++ algorithm header file.

Change-Id: Ib88f810a048dba18526b7c7cf42d87ba095a27be
Signed-off-by: Ratan Gupta <ratagupt@in.ibm.com>
diff --git a/src/count.hpp b/src/count.hpp
index a588ccc..f7b809f 100644
--- a/src/count.hpp
+++ b/src/count.hpp
@@ -3,6 +3,8 @@
 #include "callback.hpp"
 #include "data_types.hpp"
 
+#include <algorithm>
+
 namespace phosphor
 {
 namespace dbus