net/softnic: fix undefined device info fields

net/softnic: fix undefined device info fields

The memcpy operation overwrites the device info fields set
by ethdev API and leaves the device field undefined.
Thus, replaces memcpy by only updating the required fields
at the driver layer.

error log: testpmd> show port info 1

**** Infos for port 1  ****
MAC address: 00:00:00:00:00:00
Device name: net_softnic0

Segmentation fault.
port_infos_display (port_id=1) at /dpdk/app/test-pmd/config.c:418
if (dev_info.device->devargs && dev_info.device->devargs->args)

Fixes: cc6d421574fe ("net/softnic: add softnic PMD")
Cc: stable@dpdk.org
Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>