intel.lua: add_tso_test_buffer: better adherence to original test spec : 4096 packet [54 (header) + 4042 (payload)] sent using mss = 1442,  max frame size = 54 + 1442 + 4 = 1500 bytes, total bytes tx-ed = 2 * (54 + 1442 + 4) + (54 + (4042 - 2*1442) + 4) = 4216 bytes