drm_hwcomposer: Rename DrmResources to DrmDevice

DrmDevice is a better name to reflect the fact that DrmResources/
DrmDevice can handle just one dri node.

Suggested here [1] by Sean Paul.
[1] https://lists.freedesktop.org/archives/dri-devel/2018-April/173290.html

Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
diff --git a/drmdisplaycompositor.h b/drmdisplaycompositor.h
index 0d85949..1866d43 100644
--- a/drmdisplaycompositor.h
+++ b/drmdisplaycompositor.h
@@ -40,7 +40,7 @@
   DrmDisplayCompositor();
   ~DrmDisplayCompositor();
 
-  int Init(DrmResources *drm, int display);
+  int Init(DrmDevice *drm, int display);
 
   std::unique_ptr<DrmDisplayComposition> CreateComposition() const;
   int ApplyComposition(std::unique_ptr<DrmDisplayComposition> composition);
@@ -78,7 +78,7 @@
 
   std::tuple<int, uint32_t> CreateModeBlob(const DrmMode &mode);
 
-  DrmResources *drm_;
+  DrmDevice *drm_;
   int display_;
 
   std::unique_ptr<DrmDisplayComposition> active_composition_;