drm/i915: Only run idle processing from i915_gem_retire_requests_worker

drm/i915: Only run idle processing from i915_gem_retire_requests_worker

commit 725a5b54028916cd2511a251c5b5b13d1715addc upstream.

When adding the fb idle detection to mark-inactive, it was forgotten
that userspace can drive the processing of retire-requests. We assumed
that it would be principally driven by the retire requests worker,
running once every second whilst active and so we would get the deferred
timer for free. Instead we spend too many CPU cycles reclocking the LVDS
preventing real work from being done.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reported-and-tested-by: Alexander Lam <lambchop468@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=58843
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>