FDT helper functions: Respect architecture in PSCI function IDs

FDT helper functions: Respect architecture in PSCI function IDs

PSCI uses different function IDs for CPU_SUSPEND and CPU_ON, depending on
the architecture used (AArch64 or AArch32).
For recent PSCI versions the client will determine the right version,
but for PSCI v0.1 we need to put some ID in the DT node. At the moment
we always add the 64-bit IDs, which is not correct if TF-A is built for
AArch32.

Use the function IDs matching the TF-A build architecture, for the two
IDs where this differs. This only affects legacy OSes using PSCI v0.1.

On the way remove the sys_poweroff and sys_reset properties, which were
never described in the official PSCI DT binding.

Change-Id: If77bc6daec215faeb2dc67112e765aacafd17f33
Signed-off-by: Andre Przywara <[email protected]>