iwlwifi: mvm: fix ROC reference accounting

commit b112889c ("iwlwifi: mvm: add Aux ROC request/response flow")
added aux ROC flow in addition to the existing ROC flow. While doing
it, it moved the ROC reference release to a common work item, which
is being called for both the ROC and aux ROC flows.

This resulted in invalid reference accounting, as no reference was
taken in case of aux ROC, while a reference was released on completion.

Fix it by adding a reference for the aux ROC as well, and release
only the relevant references on completion (according to the set bits).

While at it, convert cancel_work_sync() to flush_work(), in order
to make sure the references are being cleaned properly.

Fixes: b112889c

 ("iwlwifi: mvm: add Aux ROC request/response flow")
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>