ath10k: cancel rx worker in hif_stop for SDIO

The rx worker of SDIO should be cancelled after disable interrupt, and
release rx sk_buff in queue, otherwise the rx worker maybe still run
after hif_stop. And it should be cancelled before napi_synchronize in
hif_stop, because the rx worker of SDIO will call napi_schedule, it
should have no napi_schedule before napi_synchronize, otherwise it
lead napi_synchronize wait untill napi_complete.

Tested-on: QCA6174 hw3.2 SDIO WLAN.RMH.4.4.1-00049

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1604558036-4056-1-git-send-email-wgong@codeaurora.org