enb: incorporate number of carriers into ue_max_rate() API

this allows the enb to calculate the max rate in a single
spot rather than each test individually

Change-Id: Id225a986e0b271cf9c057c74c9aefd6c7f3d39d6
diff --git a/src/osmo_gsm_tester/obj/enb.py b/src/osmo_gsm_tester/obj/enb.py
index 85aca35..6384f15 100644
--- a/src/osmo_gsm_tester/obj/enb.py
+++ b/src/osmo_gsm_tester/obj/enb.py
@@ -213,7 +213,7 @@
         pass
 
     @abstractmethod
-    def ue_max_rate(self, downlink=True):
+    def ue_max_rate(self, downlink=True, num_carriers=1):
         pass
 
     @abstractmethod