enb: Add modifiers for num_prb

Change-Id: I0b8c834f1c67cc4bf4d07d03358ba2012331cbde
diff --git a/src/osmo_gsm_tester/resource.py b/src/osmo_gsm_tester/resource.py
index e8ca859..31e8463 100644
--- a/src/osmo_gsm_tester/resource.py
+++ b/src/osmo_gsm_tester/resource.py
@@ -89,6 +89,7 @@
         'enb[].type': schema.STR,
         'enb[].remote_user': schema.STR,
         'enb[].addr': schema.IPV4,
+        'enb[].num_prb': schema.UINT,
         'enb[].rf_dev_type': schema.STR,
         'enb[].rf_dev_args': schema.STR,
         'arfcn[].arfcn': schema.INT,