ixgbe: cleanup ixgbe_setup_gpie() for X540

The X540 thermal sensor interrupt isn't a General Purpose Interrupt
so doesn't need to be enabled in ixgbe_setup_gpie().  Likewise X540 doesn't
use the SDP0 for thermal sensor so it doesn't need to be enabled for any
device other than 82599.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>