mm-video: vidc: Setprop command support for uncache buffers
The video playback buffers can be allocated as uncache buffers
when requried using below setprop command

setprop persist.video.mem.usecache 0

The video recording buffers can be allocated as uncache buffers
when required using below setprop command

setprop persist.camera.mem.usecache 0

By default all the buffers are allocated as cache buffers.

Change-Id: Ic68414cf42afa2b8467a821fae31bda3fd10045f

Patch manually applied by me; original author is Maheshwar Ajja.
vidc: Replace ION_FLAG_CACHED with CACHED
vidc: Use ION for decoder