avr32: Hammerhead board support

The Hammerhead platform is built around a AVR32 32-bit microcontroller
from Atmel.  It offers versatile peripherals, such as ethernet, usb
device, usb host etc.

The board also incooperates a power supply and is a Power over Ethernet
(PoE) Powered Device (PD).

Additonally, a Cyclone III FPGA from Altera is integrated on the board.
The FPGA is mapped into the 32-bit AVR memory bus. The FPGA offers two
DDR2 SDRAM interfaces, which will cover even the most exceptional need
of memory bandwidth. Together with the onboard video decoder the board
is ready for video processing.

This patch does include the basic support for the fpga device driver,
but not the device driver itself.

Signed-off-by: Alex Raimondi <mailinglist@miromico.ch>
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>