gbproxy: Move peer definitions to gb_proxy_peer.c

This patch moves the peer related definitions from gb_proxy.c to
gb_proxy_peer.c and adjusts the prefix of each global symbol to
gbproxy_:

Peer definitions (prefix adjusted to gbproxy_):
  peer_ctr_description -> gprs/gb_proxy_peer.c (static)
  peer_ctrg_desc -> gprs/gb_proxy_peer.c (static)
  *peer_by_* -> gprs/gb_proxy_peer.c
  gbproxy_peer_alloc -> gprs/gb_proxy_peer.c
  gbproxy_peer_free -> gprs/gb_proxy_peer.c
  gbprox_cleanup_peers -> gprs/gb_proxy_peer.c

Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
index 1d89ef6..a8a84af 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -1203,7 +1203,7 @@
 	gprs_dump_nsi(nsi);
 	dump_peers(stdout, 0, 0, &gbcfg);
 
-	peer = gbprox_peer_by_nsei(&gbcfg, 0x1000);
+	peer = gbproxy_peer_by_nsei(&gbcfg, 0x1000);
 	OSMO_ASSERT(peer != NULL);
 
 	send_bssgp_reset_ack(nsi, &sgsn_peer, 0x1002);
@@ -1423,7 +1423,7 @@
 	setup_ns(nsi, &bss_peer[0], 0x1001, 0x1000);
 	setup_bssgp(nsi, &bss_peer[0], 0x1002);
 
-	peer = gbprox_peer_by_nsei(&gbcfg, 0x1000);
+	peer = gbproxy_peer_by_nsei(&gbcfg, 0x1000);
 	OSMO_ASSERT(peer != NULL);
 
 	send_bssgp_reset_ack(nsi, &sgsn_peer, 0x1002);