ixgbe: Remove unnecessary usages of memset

Replace memsets of 1 byte with simple assignment.
Issue found with checkpatch.pl

Signed-off-by: Suraj Upadhyay <usuraj35@gmail.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>