WALT has check_for_migration() that calls find_energy_efficient_cpu().
But with CASS, using find_energy_efficient_cpu() is irrelevant. Since
check_for_migration() also doesn't prove to be much useful even without
the reference to find_energy_efficient_cpu(), do not use it while using
CASS with WALT. There's no need to use IS_ENABLED() for CONFIG_SCHED_WALT
here since the function is already guarded with CONFIG_SCHED_WALT.
Signed-off-by: Tashfin Shakeer Rhythm <tashfinshakeerrhythm@gmail.com>