extract a link status of PHY when parent driver is re(4).
RGEPHY_MII_SSR register does not seem to report correct PHY status
on some integrated PHYs used with re(4).
Unfortunately, RealTek PHYs have no additional information to
differentiate integrated PHYs from external ones so relying on PHY
model number is not enough to know that. However, it seems
RGEPHY_MII_SSR register exists for external RealTek PHYs so
checking parent driver would be good indication to know which PHY
was used. In other words, for non-re(4) controllers, the PHY is
external one and its revision number is greater than or equal to 2.
This change fixes intermittent link UP/DOWN messages reported on
RTL8169 controller.
Also, mii_attach(9) is tried after setting interface name since
rgephy(4) have to know parent driver name.
PR: kern/165509
fed3ed710d