virtio: fix crash in secondary process
virtio: fix crash in secondary process

It needs Rx function even in the case of secondary process,
and it also needs check if it supports mergeable feature or not.

Signed-off-by: Changchun Ouyang <593bf1f161e79772915ea885e47cf0e95f4498c0@intel.com>

msune/dpdk,mixja/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,venkynv/dpdk-mirror,mixja/dpdk,tsphillips/dpdk-fork,msune/dpdk,venkynv/dpdk-mirror,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,john-mcnamara-intel/dpdk,tsphillips/dpdk-fork,msune/dpdk,mixja/dpdk,msune/dpdk,mixja/dpdk,tsphillips/dpdk-fork,john-mcnamara-intel/dpdk,tsphillips/dpdk-fork