Updated Amlogic aml8726-m6 and aml8726-m8 support files

[John Wehle]

> if you change mii_mediachg() to mii_pollstat() in the interrupt hander,
> then changing media works stable for you ?

It seemed to with limited testing.  However there were other issues to
be resolved (e.g. some bit flag differences between the Altera and the
Amlogic) ... getting the dwc working reliable on the Amlogic was / is
still a work in progress.

I'm incline to continue porting the NetBSD driver since it's known to
be stable with the Allwinner / Amlogic silicon (i.e. it already has any
magical register poking that might be necessary).  Once it's working on
FreeBSD with the Amlogic SoC we can then compare / contrast the two
drivers to see:

  1) If it's reasonable to merge them into one driver

  2) Exactly what there is which needs to be merged

-- John