switch to dynamically allocated BTS and TRX data structures

This makes it much easier to do run-time configuration using the vty
interface.
diff --git a/openbsc/src/ipaccess-config.c b/openbsc/src/ipaccess-config.c
index cc8a6c9..d3f3176 100644
--- a/openbsc/src/ipaccess-config.c
+++ b/openbsc/src/ipaccess-config.c
@@ -170,11 +170,12 @@
 		exit(2);
 	}
 
-	gsmnet = gsm_network_init(1, GSM_BTS_TYPE_NANOBTS_900, 1, 1, NULL);
+	gsmnet = gsm_network_init(1, 1, NULL);
 	if (!gsmnet)
 		exit(1);
 
-	bts = &gsmnet->bts[0];
+	bts = gsm_bts_alloc(gsmnet, GSM_BTS_TYPE_NANOBTS_900, HARDCODED_TSC,
+				HARDCODED_BSIC);
 	
 	printf("Trying to connect to ip.access BTS ...\n");