drm_hwcomposer: Purge drm_ from drmdisplaycompositor

Having DrmDevice as a member in DrmDisplayCompositor is redundant,
since that could be always retrieved by calling:
resource_manager_->GetDrmDevice(display_)

Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
diff --git a/drmhwctwo.cpp b/drmhwctwo.cpp
index a6b48e2..c81828f 100644
--- a/drmhwctwo.cpp
+++ b/drmhwctwo.cpp
@@ -173,7 +173,7 @@
   }
 
   int display = static_cast<int>(handle_);
-  int ret = compositor_.Init(resource_manager_, drm_, display);
+  int ret = compositor_.Init(resource_manager_, display);
   if (ret) {
     ALOGE("Failed display compositor init for display %d (%d)", display, ret);
     return HWC2::Error::NoResources;