COMPMID-418 Add check and fix comments after preprocessor conditions

Change-Id: I1353fd652ee180e3931e58b4ce13d651a48c7e2c
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/79567
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
Reviewed-by: Moritz Pflanzer <moritz.pflanzer@arm.com>
diff --git a/arm_compute/core/NEON/kernels/NENonMaximaSuppression3x3Kernel.h b/arm_compute/core/NEON/kernels/NENonMaximaSuppression3x3Kernel.h
index 0daae59..68f11d8 100644
--- a/arm_compute/core/NEON/kernels/NENonMaximaSuppression3x3Kernel.h
+++ b/arm_compute/core/NEON/kernels/NENonMaximaSuppression3x3Kernel.h
@@ -92,8 +92,8 @@
      */
     void configure(const ITensor *input, ITensor *output, bool border_undefined);
 };
-#else
+#else  /* ARM_COMPUTE_ENABLE_FP16 */
 using NENonMaximaSuppression3x3FP16Kernel = NENonMaximaSuppression3x3Kernel;
-#endif
+#endif /* ARM_COMPUTE_ENABLE_FP16 */
 }
 #endif /* _ARM_COMPUTE_NENONMAXIMASUPPRESSION3x3KERNEL_H__ */