wifi: ath12k: refactor ath12k_mac_op_start()

wifi: ath12k: refactor ath12k_mac_op_start()

To support single wiphy abstraction, introduce link/radio specific helper
function in the mac80211 callback start(). This way, the callback can be
extended to handle multiple link/radio in the future.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4

Signed-off-by: Karthikeyan Periyasamy <quic_periyasa@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240103063731.3356060-5-quic_periyasa@quicinc.com