drm_hwcomposer: Move HwcDisplay out of DrmHwcTwo class

Reduces code complexity.

Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/35
Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/backend/BackendManager.cpp b/backend/BackendManager.cpp
index 0577e2f..aadef36 100644
--- a/backend/BackendManager.cpp
+++ b/backend/BackendManager.cpp
@@ -41,7 +41,7 @@
   return 0;
 }
 
-int BackendManager::SetBackendForDisplay(DrmHwcTwo::HwcDisplay *display) {
+int BackendManager::SetBackendForDisplay(HwcDisplay *display) {
   std::string driver_name(display->drm()->GetName());
   char backend_override[PROPERTY_VALUE_MAX];
   property_get("vendor.hwc.backend_override", backend_override,