ixgbe: LINKS2 is not a valid register for 82598

82598 shouldn't try and access LINKS2 while configuring
link and flow control.  This is an 82599-only register.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>