drm_hwcomposer: Move eglCreateImageKHR into Importer

Since NV has a "special" nonstandard way to get an EGLImage from a
handle, move this into Importer where the other NV specialness is
abstracted.  For the platformdrmgeneric case, use the dmabuf EGL
Extension.

Change-Id: I5353f4c95f55174df55ba92931cdc9a9eab80dca
Signed-off-by: Robert Foss <robert.foss@collabora.com>
diff --git a/glworker.h b/glworker.h
index 222cf6f..158490c 100644
--- a/glworker.h
+++ b/glworker.h
@@ -43,7 +43,8 @@
 
   int Init();
   int Composite(DrmHwcLayer *layers, DrmCompositionRegion *regions,
-                size_t num_regions, const sp<GraphicBuffer> &framebuffer);
+                size_t num_regions, const sp<GraphicBuffer> &framebuffer,
+                Importer *importer);
   void Finish();
 
  private: