iwlwifi: mvm: remove set but unused variable in iwl_mvm_roc_done_wk

Since the removal of non-DQA code, we don't need the queues
variable any more. Remove it.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>