ARM: dts: imx: add devicetree for Kobo Libra H2O

This adds a devicetree for the Kobo Libra H2O Ebook reader. It is based on
boards called e70k02. It is equipped with an imx6sll SoC.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>