ixgbe: Change some uses of strncpy to strlcpy

Change some uses of strncpy to use the more appropriate strlcpy
when clearing is not needed to prevent information leakage. Also
change some length arguments to use the preferred sizeof form.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>