ARM: mvebu: add suspend/resume DT information for Armada XP GP

ARM: mvebu: add suspend/resume DT information for Armada XP GP

This commit improves the Armada XP GP Device Tree description to
describe the 3 GPIOs that are used to connect the SoC to the PIC
micro-controller that we talk to shutdown the SoC when entering
suspend to RAM.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Link: https://lkml.kernel.org/r/1416585613-2113-15-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>