wifi: ath12k: avoid repeated hw access from ar

Currently, the helper functions are accessing mac80211 hw data from the
radio (ar) structure repeatedly. So optimize these helper functions by
storing mac80211 hw data locally and accessing it directly.

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

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://lore.kernel.org/r/20231120235812.2602198-3-quic_periyasa@quicinc.com