ath10k: change swap mail box config for UTF mode of SDIO

For SDIO chip, it does not have HTT connect step in boot phase of UTF
mode, so it does not need the swap configuration for UTF mode, otherwise
it will trigger UTF load fail. For normal mode, it is swap between HTT
and WMI, for UTF mode, it does not have HTT, so it can not swap between
HTT and WMI.

Disable swap mail box for UTF mode will let UTF mode load success.

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>