ath11k: re-enable ht_cap/vht_cap for 5G band for WCN6855

WCN6855 uses single_pdev_only, so it supports both the 5G and 6G bands
in the same ath11k/pdev and it needs to enable ht_cap/vht_cap for the 5G
band, otherwise it will downgrade to non-HT mode for the 5G band. Some
chips like QCN9074 only support the 6G band, not the 5G band, and use
the flag ar->supports_6ghz which is true to discard ht_cap/vht_cap.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210804181217.88751-2-jouni@codeaurora.org