ixgbe: fix typo in enumeration name

This was pointed out to me by Xiaojun Zhang on Source Forge.

CC: Xiaojun Zhang <zhangxiaojun@sourceforge.net>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>