ixgbe: Fix comments that are out of date or formatted incorrectly

This patch corrects several comments that are either incorrect or formatted
incorrectly for multiline comments.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>