ath11k: set credit_update flag for flow controlled ep only

Firmware will check all the pipes before entering WoW mode during suspend. If
ATH11K_HTC_FLAG_NEED_CREDIT_UPDATE is set, firmware treats this pipe needed to
return credit even though it's actually not required. If any pipe needs to
return credit, the suspend_complete message doesn't send to host but is
dropped.  So host gets time out and WoW suspend failed.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1
Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1607708150-21066-8-git-send-email-kvalo@codeaurora.org

drivers/net/wireless/ath/ath11k/htc.c

@@ -60,8 +60,10 @@ static void ath11k_htc_prepare_tx_skb(struct ath11k_htc_ep *ep,
 	memset(hdr, 0, sizeof(*hdr));
 	hdr->htc_info = FIELD_PREP(HTC_HDR_ENDPOINTID, ep->eid) |
 			FIELD_PREP(HTC_HDR_PAYLOADLEN,
-				   (skb->len - sizeof(*hdr))) |
-			FIELD_PREP(HTC_HDR_FLAGS,
+				   (skb->len - sizeof(*hdr)));
+
+	if (ep->tx_credit_flow_enabled)
+		hdr->htc_info |= FIELD_PREP(HTC_HDR_FLAGS,
 					    ATH11K_HTC_FLAG_NEED_CREDIT_UPDATE);
 
 	spin_lock_bh(&ep->htc->tx_lock);