igb: Some fine tuning

This patch does the following:

1. Changes the existing supported device id's so now DH89xxCC is not supported when EEPROM is not read.
2. Adds two more device ids for DH89xxCC in backplane mode and SFP.
3. Driver now initializes previously possibly uninitialized value in igb_reset_mdicnfg_82580().

Signed-off-by: Joseph Gasparakis <joseph.gasparakis@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/igb/e1000_82575.c b/drivers/net/igb/e1000_82575.c
index bc183f5..50f6e96 100644
--- a/drivers/net/igb/e1000_82575.c
+++ b/drivers/net/igb/e1000_82575.c
@@ -134,6 +134,8 @@
 	case E1000_DEV_ID_82580_COPPER_DUAL:
 	case E1000_DEV_ID_DH89XXCC_SGMII:
 	case E1000_DEV_ID_DH89XXCC_SERDES:
+	case E1000_DEV_ID_DH89XXCC_BACKPLANE:
+	case E1000_DEV_ID_DH89XXCC_SFP:
 		mac->type = e1000_82580;
 		break;
 	case E1000_DEV_ID_I350_COPPER:
@@ -1578,7 +1580,7 @@
 {
 	s32 ret_val = 0;
 	u32 mdicnfg;
-	u16 nvm_data;
+	u16 nvm_data = 0;
 
 	if (hw->mac.type != e1000_82580)
 		goto out;