drm/i915: Delay first PSR activation.

drm/i915: Delay first PSR activation.

When debuging the frozen screen caused by HW tracking with low
power state I noticed that if we keep moving the mouse non stop
you will miss the screen updates for a while. At least
until we stop moving the mouse for a small time and move again.

The actual enabling should happen immediately after
Display Port enabling sequence finished with links trained and
everything enabled. However we face many issues when enabling PSR
right after a modeset.

On VLV/CHV we face blank screens on this scenario and on HSW+
we face a recoverable frozen screen, at least until next
exit-activate sequence.

Another workaround for the same issue here would be to increase
re-enable idle time from 100 to 500 as we did for VLV/CHV.
However this patch workaround this issue in a better
way since it doesn't reduce PSR residency and also
allow us to reduce the delay time between re-enables at least
on VLV/CHV.

This is also important to make the sysfs toggle working properly.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>