don't re-implement osmo_talloc_replace_string()

osmo_talloc_replace_string() was introducd into libosmocore in 2014, see
commit f3c7e85d05f7b2b7bf093162b776f71b2bc6420d

There's no reason for us to re-implement this as bsc_replace_string
here.

Change-Id: I6d2fcaabbc74730f6f491a2b2d5c784ccafc6602
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c b/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
index 3453758..128ea65 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
@@ -362,7 +362,7 @@
 		return CTRL_CMD_ERROR;
 
 	if (strcmp(bsc_variable, "access-list-name") == 0) {
-		bsc_replace_string(bsc_cfg, &bsc_cfg->acc_lst_name, cmd->value);
+		osmo_talloc_replace_string(bsc_cfg, &bsc_cfg->acc_lst_name, cmd->value);
 		cmd->reply = talloc_asprintf(cmd, "%s",
 				bsc_cfg->acc_lst_name ? bsc_cfg->acc_lst_name : "");
 		return CTRL_CMD_REPLY;