well as is, so - just fetch current status upon MII_TICK.
Also do IFM_INST verification at the top of *_service() then doing it
separately for every case in switch.
acphy: do not read MII_ACPHY_DIAG twice, there is nothing latching.
qsphy: always fetch actual link status from MII_QSPHY_PCTL.
MFC after: 1 week
Rename mii_phy_auto_stop() mii_phy_down().
Introduce mii_down(), use it from nge. Do not indirect it to 19 identical
case's in 19 switchstatements like NetBSD did.
. Make internal service routines static.
. Use a consistent ordering of checks in MII_TICK. Do the work in the
mii_phy_tick() subroutine if appropriate.
. Call mii_phy_update() to trigger the callbacks.
