drm/i915/gen9: Add ddb changes to atomic debug output

Finally, add some debugging output for ddb changes in the atomic debug
output. This makes it a lot easier to spot bugs from incorrect ddb
allocations.

Signed-off-by: Lyude <cpaul@redhat.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476480722-13015-7-git-send-email-cpaul@redhat.com