ixgbe: fix potential null dereference

This patch adds a default case which goes to the next loop iteration
in the case where p is not set, preventing p from being dereferenced.

Signed-off-by: Josh Hay <joshua.a.hay@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
index 216203e..bafd141 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
@@ -1040,6 +1040,9 @@
 			p = (char *) adapter +
 					ixgbe_gstrings_stats[i].stat_offset;
 			break;
+		default:
+			data[i] = 0;
+			continue;
 		}
 
 		data[i] = (ixgbe_gstrings_stats[i].sizeof_stat ==