igb: Add check for invalid size to igb_get_invariants_82575()

Recent commits have changed how EEPROM size is checked and if the size
word is misconfigured, the driver will fail to load.  This patch adds a
check for invalid size word in the EEPROM and uses default size instead
for 82576 parts.

Reported-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/igb/e1000_82575.c

@@ -244,6 +244,14 @@ static s32 igb_get_invariants_82575(struct e1000_hw *hw)
 	 */
 	size += NVM_WORD_SIZE_BASE_SHIFT;
 
+	/*
+	 * Check for invalid size
+	 */
+	if ((hw->mac.type == e1000_82576) && (size > 15)) {
+		printk("igb: The NVM size is not valid, "
+			"defaulting to 32K.\n");
+		size = 15;
+	}
 	nvm->word_size = 1 << size;
 	if (nvm->word_size == (1 << 15))
 		nvm->page_size = 128;