si: Another round of PCS related fixes

Inside the SI1 rest_octets we will need to indicate if the ARFCN
is band 1800 or 1900. If the BTS is either 850 or 1900 we assume
we are running a PCS network, otherwise it is a DCS network.

The band indicator is not documented in GSM 04.08 but it is in the
GSM 05.14 version 6.1.0 Release 1997.
diff --git a/openbsc/include/openbsc/rest_octets.h b/openbsc/include/openbsc/rest_octets.h
index 2d16a1f..56d4e0d 100644
--- a/openbsc/include/openbsc/rest_octets.h
+++ b/openbsc/include/openbsc/rest_octets.h
@@ -4,7 +4,7 @@
 #include <openbsc/gsm_04_08.h>
 
 /* generate SI1 rest octets */
-int rest_octets_si1(uint8_t *data, uint8_t *nch_pos);
+int rest_octets_si1(uint8_t *data, uint8_t *nch_pos, int is1800_net);
 
 struct gsm48_si_selection_params {
 	uint16_t penalty_time:5,