[paging] Keep a copy of the Control Channel Description in the bts struct

- Initialize Control Channel Description of SI3 
- Patch the table
- Setting ATT now is easy
- Paging can now extract all required information... to determine
  the right paging group.

diff --git a/include/openbsc/gsm_data.h b/include/openbsc/gsm_data.h
index 2173c51..621f116 100644
--- a/include/openbsc/gsm_data.h
+++ b/include/openbsc/gsm_data.h
@@ -4,6 +4,7 @@
 #include <sys/types.h>
 
 #include <openbsc/timer.h>
+#include <openbsc/gsm_04_08.h>
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 
@@ -191,6 +192,8 @@
 	/* number of this BTS on given E1 link */
 	u_int8_t bts_nr;
 
+	struct gsm48_control_channel_descr chan_desc;
+
 	/* CCCH is on C0 */
 	struct gsm_bts_trx *c0;
 	/* transceivers */