net/irda: remove pointless assignment/check

We've already set sk to sock->sk and dereferenced it, so if it's NULL
we would have crashed already. Moreover, if it was NULL we would have
crashed anyway when jumping to 'out' and trying to unlock the sock.
Furthermore, if we had assigned a different value to 'sk' we would
have been calling lock_sock() and release_sock() on different sockets.

My conclusion is that these two lines are complete nonsense and only
serve to confuse the reader.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>