netdev-dpdk: Fix variables naming in set_admin_state function.

netdev-dpdk: Fix variables naming in set_admin_state function.

Function 'netdev_dpdk_set_admin_state()' was missed while fixing
variables naming according to the following convention:

    'struct netdev':'netdev'
    'struct netdev_dpdk':'dev'
    'struct netdev_rxq':'rxq'
    'struct netdev_rxq_dpdk':'rx'

Fixes: d46285a2206f ("netdev-dpdk: Consistent variable naming.")
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: Ian Stokess <ian.stokes@intel.com>