wifi: ath11k: support usercase-specific firmware overrides

wifi: ath11k: support usercase-specific firmware overrides

Introduce 'firmware-name' property to allow end-users and/or integrators to
decide which usecase-specific firmware to run on the WCN6855. This is
necessary due to resource limitations such as memory capacity and CPU
capability, or performance and power optimization for different application
scenarios.

Currently, there are two firmwares, both files can be executed
interchangeably.
For example:

- ath11k/WCN6855/hw2.0/amss.bin,
  ath11k/WCN6855/hw2.0/m3.bin
  ath11k/WCN6855/hw2.0/board-2.bin

- ath11k/WCN6855/hw2.0/nfa765/amss.bin,
  ath11k/WCN6855/hw2.0/nfa765/m3.bin
  ath11k/WCN6855/hw2.0/board-2.bin

The former is the default firmware, suitable for most WiFi 6 STA functions.
The latter adds support for commercial-quality SAP and optimizes power
consumption for IoT applications. And both use the same BDF/regdb data
within the main board-2.bin.

Tested-on: WCN6855 hw2.1 PCI WLAN.HSP.1.1-04479-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1

Signed-off-by: Miaoqing Pan <miaoqing.pan@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <quic_bqiang@quicinc.com>
Link: https://patch.msgid.link/20250522013444.1301330-3-miaoqing.pan@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>