hwc: vd: Dynamic dumping of frames for virtual displays

Provides a way to enable/disable dumping of virtual display
frames at runtime via binder. The dumping needs to be enabled
from a priviliged shell.

For example,
$ adb shell service call display.qservice 15 i32 3 i32 1

Here 15 is the integer code for DYNAMIC_DEBUG in IQService.h
The first parameter 3 is for DEBUG_VD
The second parameter 1 is to enable.

Change-Id: Idd62c5d9ffa6e4eb7dec585984d145bc6a421336