Clean up header inclusion in CL workloads.

Remove usage of CLFunctions.h and replace with specific header
for each function.

Signed-off-by: Matthew Bentham <Matthew.Bentham@arm.com>
Change-Id: I255a843b36a5dd8cf90a52786282192b8fe04f83
diff --git a/src/backends/cl/workloads/ClActivationWorkload.hpp b/src/backends/cl/workloads/ClActivationWorkload.hpp
index 4fdd497..3516633 100644
--- a/src/backends/cl/workloads/ClActivationWorkload.hpp
+++ b/src/backends/cl/workloads/ClActivationWorkload.hpp
@@ -7,7 +7,7 @@
 
 #include <backendsCommon/Workload.hpp>
 
-#include <arm_compute/runtime/CL/CLFunctions.h>
+#include <arm_compute/runtime/CL/functions/CLActivationLayer.h>
 
 namespace armnn
 {