sch: add missing u64 in psched_ratecfg_precompute()

It seems that commit

commit 292f1c7f
Author: Jiri Pirko <jiri@resnulli.us>
Date:   Tue Feb 12 00:12:03 2013 +0000

    sch: make htb_rate_cfg and functions around that generic

adds little regression.

Before:

# tc qdisc add dev eth0 root handle 1: htb default ffff
# tc class add dev eth0 classid 1:ffff htb rate 5Gbit
# tc -s class show dev eth0
class htb 1:ffff root prio 0 rate 5000Mbit ceil 5000Mbit burst 625b cburst
625b
 Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0
 lended: 0 borrowed: 0 giants: 0
 tokens: 31 ctokens: 31

After:

# tc qdisc add dev eth0 root handle 1: htb default ffff
# tc class add dev eth0 classid 1:ffff htb rate 5Gbit
# tc -s class show dev eth0
class htb 1:ffff root prio 0 rate 1544Mbit ceil 1544Mbit burst 625b cburst
625b
 Sent 5073 bytes 41 pkt (dropped 0, overlimits 0 requeues 0)
 rate 1976bit 2pps backlog 0b 0p requeues 0
 lended: 41 borrowed: 0 giants: 0
 tokens: 1802 ctokens: 1802

This probably due to lost u64 cast of rate parameter in
psched_ratecfg_precompute() (net/sched/sch_generic.c).

Signed-off-by: Sergey Popovich <popovich_sergei@mail.ru>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>