COMPMID-1481: CLCannyEdge still failing in some precommits

Without the check introduced by this patch, all weak edges as marked as strong
edges.

Change-Id: I874ebf22c06707bd98bd11b9be93602bfcbafa7c
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/142922
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Giorgio Arena <giorgio.arena@arm.com>
diff --git a/src/core/CL/cl_kernels/canny.cl b/src/core/CL/cl_kernels/canny.cl
index bb83eee..9bfa2f4 100644
--- a/src/core/CL/cl_kernels/canny.cl
+++ b/src/core/CL/cl_kernels/canny.cl
@@ -356,6 +356,12 @@
         return;
     }
 
+    // Return if it is a MAYBE pixel. Such pixels will become edges if near a strong edge
+    if(val <= up_thr)
+    {
+        return;
+    }
+
     // Init local stack 2
     short2 stack_L2[hysteresis_local_stack_L2] = { 0 };
     int    L2_counter                          = 0;