qdisc: meta return ENOMEM on alloc failure

Rather than returning earlier value (EINVAL), return ENOMEM if
kzalloc fails. Found while reviewing to find another EINVAL condition.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>