COMPMID-1405: Create our own gemm_native kernel / function.

Change-Id: Ie0a80bd6b4eb5632cac63ccf54bcb07d4309da19
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/140305
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/arm_compute/core/Error.h b/arm_compute/core/Error.h
index 9f51fa2..f137be6 100644
--- a/arm_compute/core/Error.h
+++ b/arm_compute/core/Error.h
@@ -157,7 +157,7 @@
  *
  * @param[in] ... Variables which are unused.
  */
-#define ARM_COMPUTE_UNUSED(...) arm_compute::ignore_unused(__VA_ARGS__) // NOLINT
+#define ARM_COMPUTE_UNUSED(...) ::arm_compute::ignore_unused(__VA_ARGS__) // NOLINT
 
 /** Creates an error with a given message
  *