ARM: at91: add kizbox board dt support.

This patch adds support for the kizbox board (based on at91sam9g20 SoC)

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>