remove unused local variable in get_rate_ctr()

Unused after 22886d9e320ecf734d2827d825a191b977f70d2c
"Fix retrieving rate_ctr over control interface"

Change-Id: Ib5411da80c4eb4f905a5ed87c60477eca2cdff42
diff --git a/src/ctrl/control_if.c b/src/ctrl/control_if.c
index 228fe35..05f6c76 100644
--- a/src/ctrl/control_if.c
+++ b/src/ctrl/control_if.c
@@ -474,7 +474,7 @@
 {
 	int intv;
 	unsigned int idx;
-	char *ctr_group, *ctr_idx, *ctr_name, *tmp, *dup, *saveptr, *interval;
+	char *ctr_group, *ctr_idx, *tmp, *dup, *saveptr, *interval;
 	struct rate_ctr_group *ctrg;
 	const struct rate_ctr *ctr;