defconfig: Add CONFIG_SCHED_MC for all arm64 targets

CONFIG_SCHED_MC enables the CPU scheduler to make better scheduling
decisions on multi-core platforms. Enable it on all MSM multi-core
targets that are not currently using it.

Change-Id: I36cffac7537fe9858bfd4fcb816f8b108c558425
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>