igb/ixgbe: Fix typo in igb_build_skb and/or ixgbe_build_skb code comment

There was a typo that I had left in the code comments for the igb and ixgbe
functions that enabled build_skb support.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>