libbsc: Update a BTS's SIs when ms_max_power is changed from VTY.

Otherwise you have to restart BTS or at least break the RSL connection
to apply the change.
diff --git a/openbsc/src/libbsc/bsc_vty.c b/openbsc/src/libbsc/bsc_vty.c
index af30f39..d126baf 100644
--- a/openbsc/src/libbsc/bsc_vty.c
+++ b/openbsc/src/libbsc/bsc_vty.c
@@ -2127,9 +2127,17 @@
       "Maximum transmit power of the MS in dBm")
 {
 	struct gsm_bts *bts = vty->index;
+	int rc;
 
 	bts->ms_max_power = atoi(argv[0]);
 
+	/* Apply setting to the BTS */
+	rc = gsm_bts_set_system_infos(bts);
+	if (rc != 0) {
+		vty_out(vty, "%% Failed updating SYSTEM INFORMATION for the BTS%s", VTY_NEWLINE);
+		return CMD_WARNING;
+	}
+
 	return CMD_SUCCESS;
 }