[dts] [PATCH V1]test_plans: update virtio related cases' testplan

[Tu, Lijuan]

> Subject: [dts] [PATCH V1]test_plans: update virtio related cases' testplan
> 
> 1. removed --socket-mem and --legacy-mem in testpmd eal parameter
> 2. removed van in qemu command since new version qemu not support this
> parameter
> 
> Signed-off-by: Xiao Qimai <qimaix.xiao at intel.com>

test_plans/vhost_enqueue_interrupt_test_plan.rst: does not exist