wifi: ath12k: Modularize driver into common and Wi-Fi 7 specific components

wifi: ath12k: Modularize driver into common and Wi-Fi 7 specific components

Split the ath12k driver into two kernel modules:

 - ath12k.ko for shared logic across multiple targets
 - ath12k_wifi7.ko for Wi-Fi 7 specific configuration and routines

The common module (ath12k.ko) must be loaded prior to any device-specific
module, as the latter depends on exported symbols from the former.

As part of this restructuring, Wi-Fi 7 specific files are moved into a
dedicated `wifi7/` directory and built as a separate module. Common
symbols are exported accordingly, with further adjustments planned
in upcoming patches to support architecture-dependent separation.

This modularization improves maintainability and scalability by enabling
clean separation of hardware-specific logic from the shared driver core.

                                          +-----------------+
                                          |                 |
                                          |   ath12k.ko     |
                                          |    (common)     |
        +---------------+                 |                 |
        |               |                 +-----------------+
        |   ath12k.ko   | ===========>
        |               |                 +------------------+
        +---------------+                 |                  |
                                          | ath12k_wifi7.ko  |
                                          | (wifi7 family)   |
                                          |                  |
                                          +------------------+

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
Tested-on: IPQ5332 hw1.0 AHB WLAN.WBE.1.3.1-00130-QCAHKSWPL_SILICONZ-1

Signed-off-by: Kiran Venkatappa <quic_kiranv@quicinc.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Link: https://patch.msgid.link/20250812-ath12k-mod-v1-10-8c9b0eb9335d@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>