ixgbe: Fix compiler warning about variable being used uninitialized

tc is still throwing a warning that is could be used
uninitialized. This fixes it, and properly formats the device ID
checks for the use of this variable.

Signed-off-by: Peter P Waskiewicz Jr <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ixgbe/ixgbe_main.c

···
 		int reg_idx = tx_ring->reg_idx;
 		int dcb_i = adapter->ring_feature[RING_F_DCB].indices;
 
-		if (adapter->hw.mac.type == ixgbe_mac_82598EB) {
+		switch (adapter->hw.mac.type) {
+		case ixgbe_mac_82598EB:
 			tc = reg_idx >> 2;
 			txoff = IXGBE_TFCS_TXOFF0;
-		} else if (adapter->hw.mac.type == ixgbe_mac_82599EB) {
+			break;
+		case ixgbe_mac_82599EB:
 			tc = 0;
 			txoff = IXGBE_TFCS_TXOFF;
 			if (dcb_i == 8) {
···
 						tc += (reg_idx - 96) >> 4;
 				}
 			}
+			break;
+		default:
+			tc = 0;
 		}
 		txoff <<= tc;
 	}