Don't lock the TX queue of a device in newer Linux kernels.

This bug was revealed by commit 5b88803. Regardless of the
NETIF_F_LLTX flag, we should not lock the TX queue of the device
ourselves with newer kernels, since we call the dev_queue_xmit()
function that locks the queue if needed.
Merge pull request #68 from srcman/linuxmodule-patches

TX queue locking fix