ice: xsk: fix VSI state check in ice_xsk_wakeup()

ICE_DOWN is dedicated for pf->state. Check for ICE_VSI_DOWN being set on
vsi->state in ice_xsk_wakeup().

Fixes: 2d4238f5

 ("ice: Add support for AF_XDP")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Tested-by: Shwetha Nagaraju <shwetha.nagaraju@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>