context CHANGE always return non-const module

Refs #1645
diff --git a/src/context.c b/src/context.c
index 1c873ed..922bb96 100644
--- a/src/context.c
+++ b/src/context.c
@@ -187,7 +187,7 @@
     return LY_SUCCESS;
 }
 
-API const struct lys_module *
+API struct lys_module *
 ly_ctx_load_module(struct ly_ctx *ctx, const char *name, const char *revision, const char **features)
 {
     struct lys_module *mod = NULL;
@@ -620,7 +620,7 @@
         uint32_t index;
 
         index = 0;
-        while ((mod = (struct lys_module *)ly_ctx_get_module_iter(ctx, &index))) {
+        while ((mod = ly_ctx_get_module_iter(ctx, &index))) {
             lysc_node_clear_all_priv(mod);
         }
     }
@@ -659,7 +659,7 @@
     return ctx->imp_clb;
 }
 
-API const struct lys_module *
+API struct lys_module *
 ly_ctx_get_module_iter(const struct ly_ctx *ctx, uint32_t *index)
 {
     LY_CHECK_ARG_RET(ctx, ctx, index, NULL);