wifi: ath12k: Restructure PCI code to common and Wi-Fi 7 specific logic

wifi: ath12k: Restructure PCI code to common and Wi-Fi 7 specific logic

Refactor pci.c to split common and hardware family specific components.
Retain shared logic such as probe and initialization sequences in common
pci.c to support reuse across device families and move Wi-Fi 7 specific
initialization and configuration to a new pci_wifi7.c file. Register
device specific routines via callbacks to keep the common PCI code
generic and extensible for future hardware families.
This improves maintainability and prepare the codebase for additional
device family support.

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

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-v1-1-8c9b0eb9335d@quicinc.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>