wifi: rtw89: initialize antenna for antenna diversity

Initialize basic antenna switch settings according to hardware module
design, and set to default antenna A. The set antenna function will be
called dynamically to switch antenna according to EVM and RSSI.

Signed-off-by: Eric Huang <echuang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230418012820.5139-6-pkshih@realtek.com