e1000e: static analysis tools complain of a possible null ptr p dereference

Adding this default case resolves the issue.

v2- Removed "break" in default case based on feedback
Signed-off-by: NBruce Allan <bruce.w.allan@intel.com>
Tested-by: NEmil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/e1000e/ethtool.c

@@ -1978,6 +1978,9 @@ static void e1000_get_ethtool_stats(struct net_device *netdev,
 			p = (char *) adapter +
 					e1000_gstrings_stats[i].stat_offset;
 			break;
+		default:
+			data[i] = 0;
+			continue;
 		}
 
 		data[i] = (e1000_gstrings_stats[i].sizeof_stat ==