drm/i915/skl: Stage the pipe DDB allocation

To correctly flush the new DDB allocation we need to know about the pipe
allocation layout inside the DDB in order to sequence the re-allocation
to not cause a newly allocated pipe to fetch from a space that was
previously allocated to another pipe.

This patch preserves the per-pipe (start,end) allocation to be used in
the flush.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index cf84b6d..01d741d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1406,6 +1406,7 @@
 }
 
 struct skl_ddb_allocation {
+	struct skl_ddb_entry pipe[I915_MAX_PIPES];
 	struct skl_ddb_entry plane[I915_MAX_PIPES][I915_MAX_PLANES];
 	struct skl_ddb_entry cursor[I915_MAX_PIPES];
 };