CpuMul changes to enable fp16 in armv8a multi_isa builds

* Moved fp16 and fp32 to their corresponding files
  src/cpu/kernels/mul/generic/neon/fp16.cpp and
  src/cpu/kernels/mul/generic/neon/fp32.cpp

* Changes in filelist.json: added a new fp16.cpp file for the float16_t kernels

* Partially resolves MLCE-1102

Change-Id: I88f24cf034c11b55ff84644b182ba76c7cb94296
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/10778
Benchmark: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
diff --git a/filelist.json b/filelist.json
index ca8b18c..a84db71 100644
--- a/filelist.json
+++ b/filelist.json
@@ -1904,7 +1904,11 @@
             "src/cpu/operators/CpuMul.cpp",
             "src/cpu/kernels/CpuMulKernel.cpp",
             "src/runtime/NEON/functions/NEPixelWiseMultiplication.cpp"
-          ]
+          ],
+        "neon":{
+          "fp16":["src/cpu/kernels/mul/generic/neon/fp16.cpp"],
+          "fp32":["src/cpu/kernels/mul/generic/neon/fp32.cpp"]
+        }
         }
       },
       "Normalize": {