wifi: rtw89: disable CSI STBC for VHT 160MHz

wifi: rtw89: disable CSI STBC for VHT 160MHz

Fix interoperability problem where CSI feedback with STBC enabled at
VHT 160MHz BW cannot be properly decoded by certain APs, causing CSI
reports to be rejected. This problem is specific to Wi-Fi 7 chips,
as Wi-Fi 6 defaults to 20MHz CSI BW. Therefore, disable STBC encoding
for CSI transmission in VHT 160MHz mode to ensure CSI feedback is
accepted by these APs and maintain smooth throughput.

Signed-off-by: Dian-Syuan Yang <dian_syuan0116@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260424072552.59220-4-pkshih@realtek.com