ARM: dts: Add support for two more Kontron SoMs N6311 and N6411

The N6311 and the N6411 SoM are similar to the Kontron N6310 SoM.
They are pin-compatible, but feature a larger RAM and NAND flash
(512MiB instead of 256MiB). Further, the N6411 has an i.MX6ULL SoC,
instead of an i.MX6UL.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>