gb: Fix gprs_active_nsvc_by_nsei()

The state matching condition is inverted. This is corrected by this
fix.

Sponsored-by: On-Waves ehf
diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index bdc7ae3..6a35ad3 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -158,8 +158,8 @@
 	struct gprs_nsvc *nsvc;
 	llist_for_each_entry(nsvc, &nsi->gprs_nsvcs, list) {
 		if (nsvc->nsei == nsei) {
-			if (nsvc->state & NSE_S_BLOCKED ||
-			    !(nsvc->state & NSE_S_ALIVE))
+			if (!(nsvc->state & NSE_S_BLOCKED) &&
+			    nsvc->state & NSE_S_ALIVE)
 				return nsvc;
 		}
 	}