net/enic: fix build with gcc 7.1

net/enic: fix build with gcc 7.1

build error:

.../dpdk/drivers/net/enic/base/vnic_dev.c:
  In function ‘vnic_dev_get_mac_addr’:
.../dpdk/drivers/net/enic/base/vnic_dev.c:470:12:
  error: ‘a0’ is used uninitialized in this function
  [-Werror=uninitialized]
  args[0] = *a0;
            ^~~
...dpdk/drivers/net/enic/base/vnic_dev.c:
  In function ‘vnic_dev_classifier’:
...dpdk/drivers/net/enic/base/vnic_dev.c:471:12:
  error: ‘a1’ may be used uninitialized in this function
  [-Werror=maybe-uninitialized]
  args[1] = *a1;
            ^~~
Fixed by providing initial values.

Fixes: 9913fbb91df0 ("enic/base: common code")
Cc: stable@dpdk.org
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>