wifi: ath12k: Move Wi-Fi 7 specific init routines to dedicated file

wifi: ath12k: Move Wi-Fi 7 specific init routines to dedicated file

Move Wi-Fi 7 specific module initialization and exit routines from core.c
to a new core_wifi7.c file. Decouple these routines from common module
entry points to improve modularity.

This restructuring is part of a broader effort to modularize the
ATH12K driver by separating common logic from hardware family-specific
implementations, improving maintainability and scalability.

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