net/vmxnet3: fix mbuf release on reset/stop

net/vmxnet3: fix mbuf release on reset/stop

During device reset/stop, vmxnet3 releases all mbufs in tx and
rx cmd ring.  For rx, we should go over all ring descriptors and
free using rte_pktmbuf_free_seg() instead of rte_pktmbuf_free()
as the metadata of the mbuf might not be properly initialized
(initialization after mempool creation is done in the rx routine)
and the mbuf should always be a single-segment one when populated.
For tx, we can use the existing way as mbuf, if any, will be a
valid one stashed in the eop.

Fixes: dfaff37fc46d ("vmxnet3: import new vmxnet3 poll mode driver implementation")

Signed-off-by: Yong Wang <yongwang@vmware.com>