Update CPU kernel implementations and guard directives

Resolves COMPMID-6023

Change-Id: I868975d14c4f98af6716726feda22405a6a4c891
Signed-off-by: Michael Tyler <michael.tyler@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/9686
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3c67987..94ae15f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -197,6 +197,7 @@
          ${CMAKE_CURRENT_SOURCE_DIR}
   PRIVATE src
           src/cpu/kernels/assembly
+          src/core/NEON/kernels/arm_gemm
           src/core/NEON/kernels/assembly
           src/core/NEON/kernels/convolution/common
           src/core/NEON/kernels/arm_conv/depthwise
@@ -223,6 +224,7 @@
          ${CMAKE_CURRENT_SOURCE_DIR}
   PRIVATE src
           src/cpu/kernels/assembly
+          src/core/NEON/kernels/arm_gemm
           src/core/NEON/kernels/assembly
           src/core/NEON/kernels/convolution/common
           src/core/NEON/kernels/arm_conv/depthwise