ath10k: enable wow feature for sdio chip

sdio does not support wow, this patch is to enable it. When system enter
sleep state, if wowlan is enabled, then sdio chip will keep power if
platform support keep power, after resume, it will not need to re-load
firmware again.

Tested with QCA6174 SDIO with firmware
WLAN.RMH.4.4.1-00029.

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>