build: remove unused headers

Remove or reduce the scope of some unused headers.  Tested by building
the code and running the unit tests.

Change-Id: I7a2b311d90352f0a949e76e9387ba552e2a186ec
Signed-off-by: Brad Bishop <bradbish@qti.qualcomm.com>
diff --git a/src/processing.cpp b/src/processing.cpp
index 842b3eb..61e6243 100644
--- a/src/processing.cpp
+++ b/src/processing.cpp
@@ -1,5 +1,7 @@
 #include "processing.hpp"
 
+#include "associations.hpp"
+
 #include <algorithm>
 #include <array>
 #include <iostream>