Build: Keep idle partition enabled on multi-core platforms

On multi-core platforms, the secure core can enter low-power state in
idle partition while no active execution is running.
TF-M may halt on multi-core platforms without the idle partition, if
SLIH or FLIH is not implemented.

Change-Id: I3a2cb8bf29aaa917dea01f2eca3b8e17cd8ba34c
Signed-off-by: David Hu <david.hu@arm.com>
1 file changed