db: Fix a bug where no pending SMS were found

The "sms send pending" VTY command did not work due a mismatch
of types. We are specifying a unsigned long long in the query
and provided DBI with a signed integer type. The result was a
failure do find any information.

Change the API to operate on unsigned long long that is matching
the id of the SMS and the Subscriber and the mismatch with the
query string is gone and pending SMS are sent.
diff --git a/openbsc/src/db.c b/openbsc/src/db.c
index 10c1d6d..9409ba5 100644
--- a/openbsc/src/db.c
+++ b/openbsc/src/db.c
@@ -1014,7 +1014,7 @@
 }
 
 /* retrieve the next unsent SMS with ID >= min_id */
-struct gsm_sms *db_sms_get_unsent(struct gsm_network *net, int min_id)
+struct gsm_sms *db_sms_get_unsent(struct gsm_network *net, unsigned long long min_id)
 {
 	dbi_result result;
 	struct gsm_sms *sms;
@@ -1041,7 +1041,7 @@
 	return sms;
 }
 
-struct gsm_sms *db_sms_get_unsent_by_subscr(struct gsm_network *net, int min_subscr_id)
+struct gsm_sms *db_sms_get_unsent_by_subscr(struct gsm_network *net, unsigned long long min_subscr_id)
 {
 	dbi_result result;
 	struct gsm_sms *sms;