wifi: ath12k: Use .mbn firmware for AHB devices

wifi: ath12k: Use .mbn firmware for AHB devices

Currently ath12k AHB devices request firmware in .mdt/.bxx split
format. AHB firmware is transitioning from the split format to a
single .mbn file.

Update ath12k to request q6_fw.mbn and iu_fw.mbn instead of q6_fw.mdt
iu_fw.mdt respectively.

Note: There is no impact to current devices since ath12k AHB support
is not yet complete and no AHB firmware files are currently present in
linux-firmware.

Tested-on: IPQ5332 hw1.0 AHB WLAN.WBE.1.7-00587-QCAHKSWPL_SILICONZ-1

Signed-off-by: Aaradhana Sahu <aaradhana.sahu@oss.qualcomm.com>
Link: https://patch.msgid.link/20260306032252.2237722-1-aaradhana.sahu@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>