cbfs: drop file_cbfs_result declaration

It is not definded anywhere.
Signed-off-by: NChristian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: NHeinrich Schuchardt <xypron.gpk@gmx.de>
Reviewed-by: NBin Meng <bmeng.cn@gmail.com>

include/cbfs.h

@@ -80,8 +80,6 @@ struct cbfs_cachenode {
 	u32 attributes_offset;
 };
 
-extern enum cbfs_result file_cbfs_result;
-
 /**
  * file_cbfs_error() - Return a string describing the most recent error
  * condition.