e1000e: fix checkpatch warning from MINMAX test

WARNING: min() should probably be min_t(unsigned int, 4, skb->data_len)

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>