ARM64: Enable multi-core scheduler support by default

Make sure that the task scheduler domain hierarchy is set-up correctly
on systems with single or multi-cluster topology.
Signed-off-by: NDietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: NPunit Agrawal <punit.agrawal@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/configs/defconfig

@@ -51,6 +51,7 @@ CONFIG_PCI=y
 CONFIG_PCI_MSI=y
 CONFIG_PCI_XGENE=y
 CONFIG_SMP=y
+CONFIG_SCHED_MC=y
 CONFIG_PREEMPT=y
 CONFIG_KSM=y
 CONFIG_TRANSPARENT_HUGEPAGE=y