ath11k: Refactor PCI code to support WCN6750

ath11k: Refactor PCI code to support WCN6750

Unlike other ATH11K PCIe devices which are enumerated by APSS
processor (Application Processor SubSystem), WCN6750 gets
enumerated by the WPSS Q6 processor (Wireless Processor SubSystem);
In simple terms, though WCN6750 is PCIe device, it is not attached
to the APSS processor, APSS will not know of such a device being
present in the system and therefore WCN6750 will be registered as
a platform device to the kernel core like other supported AHB
devices.

WCN6750 needs both AHB and PCI APIs for it's operation, it uses
AHB APIs for device probe/boot and PCI APIs for device setup and
register accesses. Because of this nature, it is referred as a
hybrid bus device.

Refactor PCI code to support hybrid bus devices like WCN6750.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1
Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.5.0.1-01100-QCAHKSWPL_SILICONZ-1
Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-00192-QCAHKSWPL_SILICONZ-1

Signed-off-by: Manikanta Pubbisetty <quic_mpubbise@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220328055714.6449-3-quic_mpubbise@quicinc.com