wifi: rtw89: 8852bt: add set_channel_rf

Add RF part of set_channel() is to configure RF registers, and then
hardware can TX/RX on specified frequency and bandwidth.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20240720021340.12102-2-pkshih@realtek.com