ARM: dts: gr8: Add support for the GR8 evaluation board

The GR8-EVB is a small board with an NextThing GR8, an Hynix MLC NAND,
an AXP209 PMIC, USB host and OTG, an SPDIF output and a connectors for CSI,
I2S and LCD.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>