realtek: phy: proper RTL8218B, RTL8214FC, RTL8214FB detection

realtek: phy: proper RTL8218B, RTL8214FC, RTL8214FB detection

Three PHYs share the same identifier. Until now we simply assume
the type depending of the bus address it is attached to. Make it
better and check the chip mode register instead.

The kernel will either detect by id/mask or by match_phy_device().
Remove the unneeded settings.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Link: https://github.com/openwrt/openwrt/pull/16457
Signed-off-by: Robert Marko <robimarko@gmail.com>