net: flow_offload: Fix memory leak for indirect flow block

The offending commit introduces a cleanup callback that is invoked
when the driver module is removed to clean up the tunnel device
flow block. But it returns on the first iteration of the for loop.
The remaining indirect flow blocks will never be freed.

Fixes: 1fac52da

 ("net: flow_offload: consolidate indirect flow_block infrastructure")
CC: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Chris Mi <cmi@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>