wifi: ath12k: enable 320 MHz bandwidth for 6 GHz band in EHT PHY capability for WCN7850

320 MHz bandwidth is reported only for single PHY mode for WCN7850, get it
from WMI_HOST_HW_MODE_SINGLE ath12k_wmi_caps_ext_params and report it for
6 GHz band.

After this patch, "iw list" shows 320 MHz support for WCN7850:

EHT Iftypes: managed
        EHT PHY Capabilities: (0xe26f090010768800):
                320MHz in 6GHz Supported
        EHT bw=320 MHz, max NSS for MCS 8-9: Rx=0, Tx=0
        EHT bw=320 MHz, max NSS for MCS 10-11: Rx=0, Tx=0
        EHT bw=320 MHz, max NSS for MCS 12-13: Rx=0, Tx=0

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4

Signed-off-by: Wen Gong <quic_wgong@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230828040420.2165-1-quic_wgong@quicinc.com