[SFQ]: Remove artificial limitation for queue limit.

This is followup to Patrick's patch. A little optimization to enqueue
routine allows to remove artificial limitation on queue length.

Plus, testing showed that hash function used by SFQ is too bad or even worse.
It does not even sweep the whole range of hash values.
Switched to Jenkins' hash.

Signed-off-by: Alexey Kuznetsov <kaber@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>