HDMI 显示测试

EC-A1684XJD4 FD 不带有显卡芯片，且主控 HDMI 输出部分并没有使用标准的
framebuffer 驱动，出厂情况下接入 HDMI 是没有显示的。

若用户要测试 HDMI 显示可接入  HDMI 接口，然后执行 "test-hdmi" 脚本：

   linaro@bm1684:~$ sudo -i
   root@bm1684:~# test-hdmi 
   found (1024, 768) @ 60 fps
   entry [0] = (1024, 768) added
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1024, 768) @ 60 fps
   found (1920, 1080) detailed timing desc
   entry [1] = (1920, 1080) added
   found (1920, 1080) detailed timing desc
   found (1920, 1080) detailed timing desc
   found (1920, 1080) detailed timing desc