tests/decode: reduce unnecessary copy
tests/decode: reduce unnecessary copy

when two fourccs are same, don't need the process of vpp.

Signed-off-by: Lin Hai <2e3a067df9da9f48e50b93ac6db863f66d51f5a2@intel.com>

lizhong1008/libyami,halleyzhao/libyami,stripes416/libyami,YuJiankang/libyami,lizhong1008/libyami,chivakker/libyami,seanvk/libyami,zhaobob/libyami,dspmeng/libyami,yizhouwei/libyami,clearlylin/libyami,uartie/libyami,zhaobob/libyami,halleyzhao/libyami,seanvk/libyami,01org/libyami,chivakker/libyami,zhaobob/libyami,uartie/libyami,clearlylin/libyami,stripes416/libyami,YuJiankang/libyami,seanvk/libyami,YuJiankang/libyami,yizhouwei/libyami,halleyzhao/libyami,halleyzhao/libyami,01org/libyami,dspmeng/libyami,yizhouwei/libyami,stripes416/libyami,01org/libyami,chivakker/libyami,dspmeng/libyami,clearlylin/libyami,uartie/libyami,lizhong1008/libyami