iwlwifi: pcie: use shadow registers for updating write pointer

The RX queues have a shadow register for the write pointer
that enables updates without grabbing NIC access. Use them
instead of the periphery registers because accessing those
is much more expensive.

Signed-off-by: Sara Sharon <sara.sharon@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
index 89f87f7..3477821 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
@@ -208,8 +208,8 @@
 
 	rxq->write_actual = round_down(rxq->write, 8);
 	if (trans->cfg->mq_rx_supported)
-		iwl_write_prph(trans, RFH_Q_FRBDCB_WIDX(rxq->id),
-			       rxq->write_actual);
+		iwl_write32(trans, RFH_Q_FRBDCB_WIDX_TRG(rxq->id),
+			    rxq->write_actual);
 	/*
 	 * write to FH_RSCSR_CHNL0_WPTR register even in MQ as a W/A to
 	 * hardware shadow registers bug - writing to RFH_Q_FRBDCB_WIDX will