ARM: dts: Add exynos5250-spring device tree

Adds initial support for the HP Chromebook 11.

Cc: Vincent Palatin <vpalatin@chromium.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Stephan van Schaik <stephan@synkhronix.com>
Signed-off-by: Andreas Faerber <afaerber@suse.de>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>