You might be able to do this via a firewall policy blocking port 137, which is the WINS name traffic port:
http://www.iss.net/security_center/advice/Services/Directory/WINS/default.htm
To block it, first create the service:
::> firewall policy service create -service WINS -protocol tcp/udp -port 137
::> firewall policy service show -service WINS
(system services firewall policy service show)
Service Name: WINS
Protocol: tcp/udp
Ports: 137
Then, apply the service to the data LIF:
::> firewall policy modify -policy data -service WINS -action deny -ip-list 0.0.0.0/0
Then see if that takes care of the broadcast... If you're seeing the broadcast on other ports, then do the same for those.