Test function test_pktmbuf_read_from_offset as one of its checks
surprisingly verifies that the following call succeeds even though
rte_pktmbuf_read never guarantees this behaviour in its documentation:

    rte_pktmbuf_read(m, hdr_len, UINT_MAX, NULL);

The reason this call succeeds is due to 32-bit unsigned integer
overflow, but it is unlikely that this behaviour is intentional and
needs testing. It is very likely instead that the check condition was
reversed by mistake. Other similar calls that follow are being correctly
verified as failing. And, there were no checks of valid offset and
excessive length combinations that would cause the call to fail.