Move CPU/GPU files from Core/Runtime to the respective backend folders

Legacy structure contained two libraries core/runtime with two backends
in each.
We reduce the core/runtime libraries to a single library thus merging
the backend files

Signed-off-by: Georgios Pinitas <georgios.pinitas@arm.com>
Change-Id: I69545765fe7a730368105cdbd067d3135ec7a174
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/6155
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
diff --git a/src/core/utils/AssemblyUtils.h b/src/core/utils/AssemblyUtils.h
index e682973..b1aee64 100644
--- a/src/core/utils/AssemblyUtils.h
+++ b/src/core/utils/AssemblyUtils.h
@@ -26,7 +26,7 @@
 
 #include "arm_compute/core/Types.h"
 #include "src/core/NEON/kernels/assembly/common.hpp"
-#include "src/core/cpu/kernels/assembly/arm_gemm.hpp"
+#include "src/cpu/kernels/assembly/arm_gemm.hpp"
 
 namespace arm_compute
 {