在AM5728 demo板上我要实现 hdmi接口的视频输出， 正在学习 github.com/.../kmsxx目录下的示例代码，我将编译出来的 kmsprint 放到demo板上运行，打印 /dev/dri/card0的相关信息：
root@am57xx-evm:~# ./kmsprint -l
Connector 0 (32) HDMI-A-1 (disconnected)
Connector 1 (36) Unknown-1 (connected)
Encoder 0 (31) TMDS
Encoder 1 (35) TMDS
Crtc 0 (34)
Crtc 1 (38) 480x272 9.000 480/2/41/2 272/2/10/2 60 (59.94)
...........
HDMI-A-1 (disconnected)，Unknown-1 (connected) 想问一下，怎样才能让HDMI-A-1 connected，而不是Unknow-1
