Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Split the chip-specific code from the generic Utopia code. This simplifies
adding of new physical chips. Now one just needs to add a .h and a .c
file for the new chip and add one line to utopia.c for that chip.

Start each of the license/copyright comments with /*-, minor shuffle of lines

Implement statistics for the PHY chips. Statistics are hold in
64-bit counters that wrap on overflow. They are collecte once per
second from the chips. Currently they can be retrieved via a sysctl phy_stats.
A write of an arbitrary value to the sysctl atomically retrieves the
statistics and clears them.

Add support for the IDT77155 Sonet/SDH PHY.

This is a driver for the physical layer chips used in ATM interfaces.
It currently supports the PMC Sierra Lite, Ultra and 622 chips and
the IDT 77105. The driver handles media options and state in a consistent
manner for ATM drivers. The next commit to the midway driver will make
it use utopia.