net_sched: sch_fq: use hash_ptr()

When I wrote sch_fq.c, hash_ptr() on 64bit arches was awful,
and I chose hash_32().

Linus Torvalds and George Spelvin fixed this issue, so we can
use hash_ptr() to get more entropy on 64bit arches with Terabytes
of memory, and avoid the cast games.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>