Configs: Enable CONFIG_SCHED_MC for powerpc

JIRA: https://issues.redhat.com/browse/RHEL-118964
Upstream Status: RHEL Only

kernel-ark commit is: dc5b2526d0d15d2aeff3a9739d87449840e9d893

Upstream consolidated some of the arch/topology scheduler configs
with 7bd291a ("sched: Unify the SCHED_{SMT,CLUSTER,MC} Kconfig")
which has the side effect of blocking the ability to disable them
selectively if the arch actually supports the feature. In RHEL we had
CONFIG_SCHED_MC off on powerpc but that is no longer possible since
we're pulling in the above commit.

Signed-off-by: Phil Auld <pauld@redhat.com>

Author: auldp