ipaccess: put the ID_GET logic for the BTS mode into the driver

This patch moves the ID_GET logic from the example file to the
ipaccess driver in BTS mode.
diff --git a/include/osmocom/abis/ipaccess.h b/include/osmocom/abis/ipaccess.h
index d4174a8..6816d87 100644
--- a/include/osmocom/abis/ipaccess.h
+++ b/include/osmocom/abis/ipaccess.h
@@ -94,6 +94,13 @@
 	uint16_t site_id;
 	uint16_t bts_id;
 	uint16_t trx_id;
+	char *unit_name;
+	char *equipvers;
+	char *swversion;
+	uint8_t mac_addr[6];
+	char *location1;
+	char *location2;
+	char *serno;
 };
 
 struct hsl_unit {