dev: fix counter_start in counter clear routine

This patch fixes counter_start value, as it should hold the cumulative
counter value whenever counter clear routine is called.

Type: fix
Fixes: 38c619115b

Change-Id: I50bf8ddcde419caf1170dfacdea03ff3d93a3327
Signed-off-by: Monendra Singh Kushwaha <kmonendra@marvell.com>
diff --git a/src/vnet/dev/counters.c b/src/vnet/dev/counters.c
index 0a1e0a7..d02839d 100644
--- a/src/vnet/dev/counters.c
+++ b/src/vnet/dev/counters.c
@@ -54,7 +54,7 @@
 {
   for (int i = 0; i < cm->n_counters; i++)
     {
-      cm->counter_start[i] = cm->counter_data[i];
+      cm->counter_start[i] += cm->counter_data[i];
       cm->counter_data[i] = 0;
     }
 }