drm_hwcomposer: Move importer.h to platform.h

We're going to need more platform-specific stuff, so lump it
all in the same header.

BUG=b/28117135
TEST=compiles

Change-Id: Idfe82e9a29a0bcd284a02b2e58af0e620fdc542b
Signed-off-by: Sean Paul <seanpaul@chromium.org>
diff --git a/nvimporter.h b/nvimporter.h
index d6033db..6c7f80a 100644
--- a/nvimporter.h
+++ b/nvimporter.h
@@ -18,7 +18,7 @@
 #define ANDROID_NV_IMPORTER_H_
 
 #include "drmresources.h"
-#include "importer.h"
+#include "platform.h"
 
 #include <stdatomic.h>