rtl8xxxu: Move PHY RF init into device specific functions

Load the RF table in init_phy_rf(), which allows for applying device
specific RF hacks in the same place. Getting rid of more ugly if ()
clutter.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>