net: txgbe: initialize num_q_vectors for MSI/INTx interrupts

In the Linux kernel, the following vulnerability has been resolved: net: txgbe: initialize num_q_vectors for MSI/INTx interrupts When using MSI/INTx interrupts, wx->num_q_vectors is uninitialized. Thus there will be kernel panic in wx_alloc_q_vectors() to allocate queue vectors.