Encoding: Add ROI example

Encoding: Add ROI example

v1:
add --roi-test for test only for ROI. default only one region(0,0,120,120) has been test.
v2:
add ROI region size check to ensure region width/height < frame_width/4 or frame_height/4 if fram width/height < 120
add ROI attrib check
v3:
check the attrib return value for ROI

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: ceciliapeng <cecilia.peng@intel.com>
Signed-off-by: Pengfei Qu <Pengfei.Qu@intel.com>