staging: rtl8723au: Reduce the usage of ODM_[GS]et_BBReg()

The vendor code has at least three different APIs for accessing
registers. One more ugly than the other. This is the start to move
away from ODM_[GS]et_BBReg()

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>