i40e: remove unneeded NULL check

i40e: remove unneeded NULL check

In i40evf_config_vlan_pvid the check for NULL for the dev value is
unnecessary, since this value is passed in from the ethdev API which
will ensure that a valid rte_eth_dev structure is provided.
Furthermore, all code paths leading to this function already use the
dev value.

Issue identified by Coverity.
  Coverity ID 13302:
  There may be a null pointer dereference, or else the comparison against
  null is unnecessary.

  In i40evf_config_vlan_pvid: All paths that lead to this null pointer
  comparison already dereference the pointer earlier

Fixes: 2b12431b5369 ("i40e: add vlan stripping and insertion to VF")

Signed-off-by: Daniel Mrzyglod <danielx.t.mrzyglod@intel.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>