Fix compiler warnings in dynamic fusion

Resolves: COMPMID-5686

Change-Id: I608c359583c44f2f04f29faddd1c6b38a381de60
Signed-off-by: SiCong Li <sicong.li@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/8562
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Jakub Sujak <jakub.sujak@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/dynamic_fusion/runtime/gpu/cl/ClKernelRuntime.h b/src/dynamic_fusion/runtime/gpu/cl/ClKernelRuntime.h
index acc2380..4787aca 100644
--- a/src/dynamic_fusion/runtime/gpu/cl/ClKernelRuntime.h
+++ b/src/dynamic_fusion/runtime/gpu/cl/ClKernelRuntime.h
@@ -35,7 +35,8 @@
 {
 namespace dynamic_fusion
 {
-struct GpuKernelSourceCode;
+/** Forward declaration */
+class GpuKernelSourceCode;
 
 /** OpenCL runtime to run a single kernel */
 class ClKernelRuntime final : public opencl::IClKernel