BTS codec pref legacy compat: allow all codecs per default

Legacy compat: we used to not check the BTS codec-pref settings upon assignment
until we added checks for the BTS codec-pref in osmo-bsc
5bc43cd107, change-id
I285234e9c81de74d9fb9907fca2c443b08537435, "codec_pref: check bts codec
support". From that commit onwards, config setups without a 'codec-pref'
potentially stop working (like all osmo-gsm-tester runs just did), because with
no codec-pref settings, now only FR is permitted, while before the patch, we
would allow any codecs as long as MSC and the overall BSC config agree on them.
So, upon BTS initialization, enable all codecs. These get reset to a more fine
grained selection IF a 'codec-support' config appears in the config file (see
bsc_vty.c).

Change-Id: I4650a1f8e350c6f74f48391f43ddfe771be01e1b

src/osmo-bsc/gsm_data.c

@@ -757,6 +757,14 @@ struct gsm_bts *gsm_bts_alloc(struct gsm_network *net, uint8_t bts_num)
 	INIT_LLIST_HEAD(&bts->abis_queue);
 	INIT_LLIST_HEAD(&bts->loc_list);
 
+	/* Enable all codecs by default. These get reset to a more fine grained selection IF a
+	 * 'codec-support' config appears in the config file (see bsc_vty.c). */
+	bts->codec = (struct bts_codec_conf){
+		.hr = 1,
+		.efr = 1,
+		.amr = 1,
+	};
+
 	return bts;
 }