minui: remove libadf since it is no longer supported

Libadf is being removed since there are no android common kernels
that support adf. Remove support from miniui.

Test: Compiles and boots
Bug: 150467766

Change-Id: Ic66ea7a012b0466810ddeb8f884150b50c8ae769
diff --git a/minui/graphics.cpp b/minui/graphics.cpp
index d34da56..dce1e61 100644
--- a/minui/graphics.cpp
+++ b/minui/graphics.cpp
@@ -25,7 +25,6 @@
 
 #include <android-base/properties.h>
 
-#include "graphics_adf.h"
 #include "graphics_drm.h"
 #include "graphics_fbdev.h"
 #include "minui/minui.h"
@@ -362,15 +361,10 @@
            ret);
   }
 
-  auto backend = std::unique_ptr<MinuiBackend>{ std::make_unique<MinuiBackendAdf>() };
+  auto backend = std::unique_ptr<MinuiBackend>{ std::make_unique<MinuiBackendDrm>() };
   gr_draw = backend->Init();
 
   if (!gr_draw) {
-    backend = std::make_unique<MinuiBackendDrm>();
-    gr_draw = backend->Init();
-  }
-
-  if (!gr_draw) {
     backend = std::make_unique<MinuiBackendFbdev>();
     gr_draw = backend->Init();
   }