libvideorender: CB1 keep last frame on flush [2/3]

PD#SWPL-158207

Problem:
add property to set keep last frame when flush.
default is keep last frame,if set to 0,westeros will
clean last frame when flush

Solution:
add property for keep last frame on flush

Verify:
AH212

Signed-off-by: le.han <le.han@amlogic.com>
Change-Id: I52f845c11dbd8b702b8e80273dc63c18b5eb4cc2
5 files changed