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