ixgbe: fix panic due to uninitialised pointer

Systems containing an 82599EB and running a backported driver from
upstream were panicing on boot.  It turns out hw->mac.ops.setup_sfp is
only set for 82599, so one should check to be sure that pointer is set
before continuing in ixgbe_sfp_config_module_task.  I verified by
inspection that the upstream driver has the same issue and also added a
check before the call in ixgbe_sfp_link_config.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>