ixgbe: make ixgbe_up and ixgbe_up_complete void functions

ixgbe_up and ixgbe_up_complete will always return 0.  Since this doesn't
provide any useful information we might as well just make them both void
and save ourselves from having to return an unused value.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>