iwlwifi: don't rely on the wr / rd pointers in DELBA flow

In the same spirit as the previous patch. Eventually this will
allow us to remove the tid_data knowledge from the transport layer.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

diff --cc drivers/net/wireless/iwlwifi/iwl-trans-pcie-tx.c
Simple merge

diff --cc drivers/net/wireless/iwlwifi/iwl-trans-pcie.c
Simple merge