[dts] [PATCH V1] tests/vswitch_sample_cbdma:modify start virtio testpmd param sync with testplan and optimize code

[Tu, Lijuan]

> Modify start virtio testpmd param sync with testplan and move create session
> and pmdout object from set_up to set_up_all in order to reduce the number of
> creation.
> 
> Signed-off-by: Ling Wei <weix.ling at intel.com>

Applied