defconfig: arm64: enable sched features for SDM855

Enable below sched features to support EAS on SDM855:
1. CONFIG_SCHED_WALT=y
2. CONFIG_SCHED_TUNE=y
3. CONFIG_DEFAULT_USE_ENERGY_AWARE=y

Change-Id: I530bd06ad39358fbfb64d739958a9ed23fa97a4e
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>