mwifiex: Add SD8997 SDIO-UART firmware

With a recent change now it is possible to detect the strapping
option on SD8997, which allows to pick up a correct firmware
for either SDIO-SDIO or SDIO-UART.

This commit enables SDIO-UART firmware on SD8997.

Signed-off-by: Andrejs Cainikovs <andrejs.cainikovs@toradex.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220422090313.125857-3-andrejs.cainikovs@toradex.com