BACKPORT: cpufreq / sched: Pass flags to cpufreq_update_util()

It is useful to know the reason why cpufreq_update_util() has just
been called and that can be passed as flags to cpufreq_update_util()
and to the ->func() callback in struct update_util_data.  However,
doing that in addition to passing the util and max arguments they
already take would be clumsy, so avoid it.

Instead, use the observation that the schedutil governor is part
of the scheduler proper, so it can access scheduler data directly.
This allows the util and max arguments of cpufreq_update_util()
and the ->func() callback in struct update_util_data to be replaced
with a flags one, but schedutil has to be modified to follow.

Thus make the schedutil governor obtain the CFS utilization
information from the scheduler and use the "RT" and "DL" flags
instead of the special utilization value of ULONG_MAX to track
updates from the RT and DL sched classes.  Make it non-modular
too to avoid having to export scheduler variables to modules at
large.

Next, update all of the other users of cpufreq_update_util()
and the ->func() callback in struct update_util_data accordingly.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
(cherry picked from commit 58919e83c85c3a3c5fb34025dc0e95ddd998c478)
diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index f62769f..884e557 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -245,7 +245,7 @@
 	  If in doubt, say N.
 
 config CPU_FREQ_GOV_SCHEDUTIL
-	tristate "'schedutil' cpufreq policy governor"
+	bool "'schedutil' cpufreq policy governor"
 	depends on CPU_FREQ && SMP
 	select CPU_FREQ_GOV_ATTR_SET
 	select IRQ_WORK
@@ -259,9 +259,6 @@
 	  frequency tipping point is at utilization/capacity equal to 80% in
 	  both cases.
 
-	  To compile this driver as a module, choose M here: the module will
-	  be called cpufreq_schedutil.
-
 	  If in doubt, say N.
 
 comment "CPU frequency scaling drivers"