Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

at91$DEV->at91_$DEV to match other Atmel drivers. Also, export
at91_rst_cpu_reset.

if_ate.c:

* Support for sam9 "EMAC" controller.
* Support for rmii interface to phy.

at91.c & at91sam9.c:

* Eliminate separate at91sam9.c file.
* Add new devices to at91sam9_devs table.

at91_machdep.c & at at91sam9_machdep.c:

* Automatic chip type determination.
* Remove compile time chip dependencies.
* Eliminate separate at91sam9_machdep.c file.

at91_pmc.c:

* Corrected support for all of the sam926? and sam9g20 chips.
* Remove compile time chip dependencies.

My apologies to Greg for taking so long to take care of it.