wifi: rtw89: Fix P2P behavior for WiFi 7 chips

Previously we used CCK rate when scanning for P2P on WiFi 7 chips.
Fix this by explicitly setting the rate to OFDM 6Mbps.

Signed-off-by: Po-Hao Huang <phhuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://msgid.link/20240522024531.11401-1-pkshih@realtek.com