DO NOT MERGE mm-video-v4l2: vidc: validate omx param/config data

Check the sanity of config/param strcuture objects
passed to get/set _ config()/parameter() methods.

Bug: 27533317
Security Vulnerability in MediaServer
omx_vdec::get_config() Can lead to arbitrary write

Change-Id: I6c3243afe12055ab94f1a1ecf758c10e88231809

Conflicts:
	mm-core/inc/OMX_QCOMExtns.h
	mm-video-v4l2/vidc/vdec/src/omx_vdec_msm8974.cpp
	mm-video-v4l2/vidc/venc/src/omx_video_base.cpp
	mm-video-v4l2/vidc/venc/src/omx_video_encoder.cpp
