net: don't decrement kobj reference count on init failure

If kobject_init_and_add failed, then the failure path would
decrement the reference count of the queue kobject whose reference
count was already zero.

Fixes: 114cf580

 ("bql: Byte queue limits")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>