rtw89: 8852c: add read/write rf register function

Using encoded address which BIT(16) is used to discriminate which region is
going to access. Illustrate the calling flow as below

rtw89_phy_write_rf_v1() -+-> rtw89_phy_write_rf()   // old interface
                         +-> rtw89_phy_write_rf_a() // new interface

Signed-off-by: Chung-Hsuan Hung <hsuan8331@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/20220317055543.40514-5-pkshih@realtek.com