dql: make dql_init return void

dql_init always returned 0, and the only place that uses it
in network core code didn't care about the return value anyway.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Acked-by: Hiroaki SHIMODA <shimoda.hiroaki@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>