Use dumpsys to collect HDMI register values in run-time

In order to debug HDMI, users can mount debugfs and dump register values for their need.


=====The following is the way to mount debugfs=====
# adb shell
# mkdir /data/debug
mkdir /data/debug
# mount -t debugfs debugfs /data/debug
mount -t debugfs debugfs /data/debug


=====The following is the way to specify hdmi registers to dump=====
# cd /data/debug/hdmi
cd /data/debug/hdmi
# echo [offset] [# of consecutive registers] > off
# cat reg


e.g. # echo 0 4 > off
echo 0 4 > off
# cat reg
cat reg
0xda8a4000: 00000007 00000000 00000000 00000000 (Then you will see 4 registers dump beginning with hdmi register 0x0000, i.e. HDMI_CTRL.)