board: add support for Mini 2440

Paul Jones documented at
http://pauljones.id.au/blog/2010/07/using-buildroot-on-a-mini2440/

 how
to use Buildroot to generate a system for the FriendlyARM Mini2440
platform. This patch integrates Paul's work into Buildroot.

Unfortunately, the kernel being 2.6.32, we can't easily use a minimal
defconfig here. The mini2440 support has been merged into more recent
kernels, but I don't have the hardware to test.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>