ice: do not setup vlan for loopback VSI

ice: do not setup vlan for loopback VSI

commit dba98e26834a71ac51b08cc4a42297e6f0b674b4 upstream.

Currently loopback test is failiing due to the error returned from
ice_vsi_vlan_setup(). Skip calling it when preparing loopback VSI.

Fixes: 9616d5b28366 ("ice: Add handler for ethtool selftest")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: George Kuruvinakunnel <george.kuruvinakunnel@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>