drm_hwcomposer: Use shared pointer type for the pipeline_ variable

The change will help with resource management in further patches.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>
diff --git a/hwc2_device/DrmHwcTwo.h b/hwc2_device/DrmHwcTwo.h
index 81c5155..8701feb 100644
--- a/hwc2_device/DrmHwcTwo.h
+++ b/hwc2_device/DrmHwcTwo.h
@@ -61,8 +61,8 @@
   }
 
   // PipelineToFrontendBindingInterface
-  bool BindDisplay(DrmDisplayPipeline *pipeline) override;
-  bool UnbindDisplay(DrmDisplayPipeline *pipeline) override;
+  bool BindDisplay(std::shared_ptr<DrmDisplayPipeline> pipeline) override;
+  bool UnbindDisplay(std::shared_ptr<DrmDisplayPipeline> pipeline) override;
   void FinalizeDisplayBinding() override;
 
   void SendVsyncEventToClient(hwc2_display_t displayid, int64_t timestamp,
@@ -75,7 +75,8 @@
 
   ResourceManager resource_manager_;
   std::map<hwc2_display_t, std::unique_ptr<HwcDisplay>> displays_;
-  std::map<DrmDisplayPipeline *, hwc2_display_t> display_handles_;
+  std::map<std::shared_ptr<DrmDisplayPipeline>, hwc2_display_t>
+      display_handles_;
 
   std::string mDumpString;