ARM: dts: at91: add smartkiz support and a common kizboxmini dtsi file

Split the existing Kizbox Mini boards into three board configuration,
the base board, the mother board and the RailDIN board.
Add a new dts file for the SmartKiz board support.

Signed-off-by: Kévin RAYMOND <k.raymond@overkiz.com>
Signed-off-by: Mickael GARDET <m.gardet@overkiz.com>
Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Link: https://lore.kernel.org/r/20191220103835.160154-2-kamel.bouhara@bootlin.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>