ath10k: change firmware file name for UTF mode of SDIO/USB

Firmware name for UTF mode of SDIO has changed from utf-2.bin to
utf-sdio-2.bin, so it need to change in ath10k, otherwise it will
fail for UTF mode.

After change the name in ath10k, it will success for UTF mode of
SDIO/USB.

Tested with QCA6174 SDIO with firmware
WLAN.RMH.4.4.1-00007-QCARMSWP-1.

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