ARM: mvebu: Warn about the wake-up sources not taken into account in suspend

ARM: mvebu: Warn about the wake-up sources not taken into account in suspend

On the Armada 370/XP/38x/39x SoCs when the suspend to ram feature is
supported, the SoCs are shutdown and will be woken up by an external
micro-controller, so there is no possibility to setup wake-up sources
from Linux. However, in standby mode, the SoCs stay powered and it is
possible to wake-up from any interrupt sources. Since when the users
configures the enabled wake-up sources there is no way to know if the
user will be doing suspend to RAM or standby, we just allow all
wake-up sources to be enabled, and only warn when entering suspend to
RAM

The purpose of this patch is to inform the user that in suspend to ram
mode, the wake-up sources won't be taken into consideration.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>