Fix up result type for bit-wise or of enum values

When combining enum values with bit-wise operators, the result is no
longer of the enum type, so we need to cast it back.

Test: local compile
Change-Id: I3697d37b612f0e29aabb46a6a958ca4ef0fed64f
diff --git a/vehicle/2.0/default/vehicle_hal_manager/SubscriptionManager.cpp b/vehicle/2.0/default/vehicle_hal_manager/SubscriptionManager.cpp
index 0d2180f..910413e 100644
--- a/vehicle/2.0/default/vehicle_hal_manager/SubscriptionManager.cpp
+++ b/vehicle/2.0/default/vehicle_hal_manager/SubscriptionManager.cpp
@@ -40,7 +40,7 @@
     }
 
     float updatedRate = std::max(oldOpts.sampleRate, newOpts.sampleRate);
-    SubscribeFlags updatedFlags = oldOpts.flags | newOpts.flags;
+    SubscribeFlags updatedFlags = SubscribeFlags(oldOpts.flags | newOpts.flags);
 
     bool updated = updatedRate > oldOpts.sampleRate
                    || updatedAreas != oldOpts.vehicleAreas