ath10k: enable firmware log by default for sdio

On SDIO chips the firmware log does not impact performance. To make it
easier to debug firmware problems keep it enabled on the firmware.

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>