e1000e: convert final strncpy() to strlcpy()

Convert the last instances of strncpy() to the preferred strlcpy().

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>