cpuidle: menu: Use shifts when calculating averages where possible

We use do_div even though the divisor will usually be a power-of-two
unless there are unusual outliers. Use shifts where possible

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpuidle: menu: Use ktime_to_us instead of reinventing the wheel

The ktime_to_us implementation is slightly better than the one implemented
in menu.c. Use it

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpuidle: menu: Call nr_iowait_cpu less times

menu_select() via inline functions calls nr_iowait_cpu() twice as much
as necessary.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
cpuidle: menu: Lookup CPU runqueues less

The menu governer makes separate lookups of the CPU runqueue to get
load and number of IO waiters but it can be done with a single lookup.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>