cpufreq: Move scheduler-related code to the sched directory

Create cpufreq.c under kernel/sched/ and move the cpufreq code
related to the scheduler to that file and to sched.h.

Redefine cpufreq_update_util() as a static inline function to avoid
function calls at its call sites in the scheduler code (as suggested
by Peter Zijlstra).

Also move the definition of struct update_util_data and declaration
of cpufreq_set_update_util_data() from include/linux/cpufreq.h to
include/linux/sched.h.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

drivers/cpufreq/cpufreq_governor.c

@@ -18,6 +18,7 @@
 
 #include <linux/export.h>
 #include <linux/kernel_stat.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 
 #include "cpufreq_governor.h"