drm/i915: Complain if we take too long under vblank evasion.

Instead of only complaining when we actually miss a vblank, always
complain if we take longer than 100 us. This will make it easier to
find cases where we potentially miss vblanks.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1488292128-14540-2-git-send-email-maarten.lankhorst@linux.intel.com


Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[mlankhorst: Add commit message.]