wifi: ath12k: fix ar->supports_6ghz usage during hw register

wifi: ath12k: fix ar->supports_6ghz usage during hw register

In the ath12k_mac_hw_register() function's context, ar is an iterator
variable, and there is no assurance that the last ar will be the one with
6 GHz enabled. Therefore, checking directly ar->supports_6ghz outside the
loop is not appropriate.

Additionally, 6 GHz lacks HT capabilities. To obtain the super set of
HT capabilities across all grouped radios, 6 GHz should be excluded.

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

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20241209185421.376381-9-kvalo@kernel.org
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>