drm_hwcomposer: Initialize HwcDisplay using DrmDisplayPIpeline

HwcDisplay can now take all necessary objects from DrmDisplayPipeline.

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/backend/Backend.cpp b/backend/Backend.cpp
index 98862ba..7d82eef 100644
--- a/backend/Backend.cpp
+++ b/backend/Backend.cpp
@@ -119,8 +119,8 @@
 std::tuple<int, int> Backend::GetExtraClientRange(
     HwcDisplay *display, const std::vector<HwcLayer *> &layers,
     int client_start, size_t client_size) {
-  size_t avail_planes = display->primary_planes().size() +
-                        display->overlay_planes().size();
+  size_t avail_planes = 1 /* primary planes count*/ +
+                        display->GetPipe().overlay_planes.size();
 
   /*
    * If more layers then planes, save one plane