arch: deprecate the AVR32 architecture

arch: deprecate the AVR32 architecture

The AVR32 architecture from Atmel is obsolete since a long time, not
supported upstream in most of the toolchain components (requires a
special version of gcc, an old version of uClibc, etc.). Until
February, Simon Dawson was making an excellent job at maintaining
AVR32 in Buildroot, and fixing all the issues caused by this
architecture. However, Simon focus has changed, and despite his call
for a new maintainer for AVR32 in Buildroot, nobody stepped up.

The issue of maintaining AVR32 is becoming worse and worse, so this
patch proposes to deprecate it for 2014.08, but keeping the support
around, to remove it for sure in 2014.11.

Cc: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>