igb: change pba size determination from if to switch statement

As additional hardware is added to the igb driver it is easier to support
the expansion via switch statements instead of using nested ifs.  For
this reason I am changing this to a switch statement.
Signed-off-by: NAlexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -888,11 +888,14 @@ void igb_reset(struct igb_adapter *adapter)
 	/* Repartition Pba for greater than 9k mtu
 	 * To take effect CTRL.RST is required.
 	 */
-	if (mac->type != e1000_82576) {
-	pba = E1000_PBA_34K;
-	}
-	else {
+	switch (mac->type) {
+	case e1000_82576:
 		pba = E1000_PBA_64K;
+		break;
+	case e1000_82575:
+	default:
+		pba = E1000_PBA_34K;
+		break;
 	}
 
 	if ((adapter->max_frame_size > ETH_FRAME_LEN + ETH_FCS_LEN) &&