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/platform.h b/platform.h
index 068499e..32d0011 100644
--- a/platform.h
+++ b/platform.h
@@ -28,7 +28,7 @@
 
 namespace android {
 
-class DrmResources;
+class DrmDevice;
 
 class Importer {
  public:
@@ -36,7 +36,7 @@
   }
 
   // Creates a platform-specific importer instance
-  static Importer *CreateInstance(DrmResources *drm);
+  static Importer *CreateInstance(DrmDevice *drm);
 
   // Imports the buffer referred to by handle into bo.
   //
@@ -88,7 +88,7 @@
   };
 
   // Creates a planner instance with platform-specific planning stages
-  static std::unique_ptr<Planner> CreateInstance(DrmResources *drm);
+  static std::unique_ptr<Planner> CreateInstance(DrmDevice *drm);
 
   // Takes a stack of layers and provisions hardware planes for them. If the
   // entire stack can't fit in hardware, FIXME