igb: correct hardware type (i210/i211) check in igb_loopback_test()

In the original code
...
 	if ((adapter->hw.mac.type == e1000_i210)
		|| (adapter->hw.mac.type == e1000_i210)) {
...
the second check of 'adapter->hw.mac.type' is pointless since it tests
for the exact same value as the first.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>