ath10k: add large size for BMI download data for SDIO

Download firmware time cost of SDIO is too long, it is about 480ms,
add large size 2048 bytes for BMI download for SDIO chip, its time
cost will reduced to 240ms.

This will optimize the download firmware time cost.

Tested with QCA6174 SDIO with firmware
WLAN.RMH.4.4.1-00017-QCARMSWP-1.

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