sched: Fix compilation issues for !CONFIG_SCHED_WALT

Below compilation issues are observed when CONFIG_SCHED_WALT is disabled.

1. kernel/sched/cpufreq_schedutil.c:408:23: \
	error: implicit declaration of function 'boosted_cpu_util'

2. kernel/sched/core_ctl.c:1291:2: \
	error: implicit declaration of function 'for_each_sched_cluster'

Fix these compilation issues by adding/updating proper checks
and dependencies as needed.

Change-Id: I59d3714a9fca0ff58758ec974f50eb5f3f00ae98
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>