In RTL8367B (RTL8367RB/RTL8367R-VB), the driver in GPL tars of the
devices with this switch directly uses the ID of external interface
as a bit offset.
We should use the same way.
ref (RTL8367B):
- ASUS RT-N56U
- TP-Link Archer C2 v1
ref (RTL8367):
- TP-Link TL-WR2543ND v1
Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>