net: sched: cls_u32: use hash_ptr() for tc_u_hash

After the change to the tp hash, we now get a build warning
on 32-bit architectures:

net/sched/cls_u32.c: In function 'tc_u_hash':
net/sched/cls_u32.c:338:17: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
  return hash_64((u64) tp->chain->block, U32_HASH_SHIFT);

Using hash_ptr() instead of hash_64() lets us drop the cast
and fixes the warning while still resulting in the same hash
value.

Fixes: 7fa9d974 ("net: sched: cls_u32: use block instead of q in tc_u_common")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>