stats: Fix the compiler warnings

Do not remove the const, include strings.h for strcmp
diff --git a/src/rate_ctr.c b/src/rate_ctr.c
index a7fc949..a0e1814 100644
--- a/src/rate_ctr.c
+++ b/src/rate_ctr.c
@@ -142,10 +142,10 @@
 	return NULL;
 }
 
-struct rate_ctr *rate_ctr_get_by_name(const struct rate_ctr_group *ctrg, const char *name)
+const struct rate_ctr *rate_ctr_get_by_name(const struct rate_ctr_group *ctrg, const char *name)
 {
 	int i;
-	struct rate_ctr_desc *ctr_desc;
+	const struct rate_ctr_desc *ctr_desc;
 
 	if (!ctrg->desc)
 		return NULL;
diff --git a/src/statistics.c b/src/statistics.c
index d1ffe52..a612140 100644
--- a/src/statistics.c
+++ b/src/statistics.c
@@ -20,8 +20,8 @@
  *
  */
 
-
 #include <sys/types.h>
+#include <string.h>
 
 #include <osmocom/core/linuxlist.h>
 #include <osmocom/core/talloc.h>