netdev-dpdk: Make get_config() report correct queue info.

With the separation of tx queue and rx queue configuration
in netdev-dpdk module, the netdev_dpdk_get_config() can no
longer report 'n_rxq' as tx queue configuration.

This commit fixes the above issue.

Reported-by: Daniele Di Proietto <ddiproietto@vmware.com>
Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Daniele Di Proietto <ddiproietto@vmware.com>
netdev-dpdk: Fix thread-safety breach.

dpdk_eth_dev_init() must be called with dpdk_mutex.  However,
netdev_dpdk_set_multiq() fails to follow this rule.  This commit
fixes this breach.

Found by clang.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Daniele Di Proietto <ddiproietto@vmware.com>