wifi: ath12k: Remove unused ath12k_base from ath12k_hw

Currently, device (ab) reference in hardware abstraction (ah)
is not used anywhere. Also, with multiple device group abstraction,
hardware abstraction would be coupled with device group abstraction
rather than single device.

Hence, remove the ab reference from hardware abstraction.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1

Signed-off-by: Harshitha Prem <quic_hprem@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240529060939.4156281-1-quic_hprem@quicinc.com