ARM: dts: Enable EC vboot context support on Peach boards

The Peach boards use the EC to store the vboot context information,
so add the corresponding properties on the EC node to indicate so.

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Emilio Lopez <emilio.lopez@collabora.co.uk>
Signed-off-by: Kukjin Kim <kgene@kernel.org>