drm/i915: Move residency calculation into intel_pm.c

Plan is to make generic residency calculation utility
function for usage outside of sysfs. As a first step
move residency calculation into intel_pm.c

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
3 files changed