SONAR suggestions - prevent truncation of arithmetic expressions

Change-Id: I4694c0c3183b991a4f0db793f584bc77a5fb7d60
diff --git a/providers/openflow/device/src/main/java/org/onosproject/provider/of/device/impl/OpenFlowDeviceProvider.java b/providers/openflow/device/src/main/java/org/onosproject/provider/of/device/impl/OpenFlowDeviceProvider.java
index 66ded21..b007af1 100644
--- a/providers/openflow/device/src/main/java/org/onosproject/provider/of/device/impl/OpenFlowDeviceProvider.java
+++ b/providers/openflow/device/src/main/java/org/onosproject/provider/of/device/impl/OpenFlowDeviceProvider.java
@@ -419,7 +419,7 @@
 
     //TODO consider renaming KBPS and MBPS (as they are used to convert by division)
     private static final long KBPS = 1_000;
-    private static final long MBPS = 1_000 * 1_000;
+    private static final long MBPS = 1_000L * 1_000L;
     private static final Frequency FREQ50 = Frequency.ofGHz(50);
     private static final Frequency FREQ191_7 = Frequency.ofGHz(191_700);
     private static final Frequency FREQ4_4 = Frequency.ofGHz(4_400);