Revert "drm/i915: Avoid stalling on pending flips for legacy cursor updates"

This reverts commit acf4e84d

.
Unfortunately this breaks the next commit with a use-after-free, so
temporarily revert until we can apply a solution.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463490484-19540-8-git-send-email-maarten.lankhorst@linux.intel.com
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>