If vmalloc() was successful, do not attempt a kmalloc_array()

Fixes: 4cf0b354 ("rhashtable: avoid large lock-array allocations")
Reported-by: NCAI Qian <caiqian@redhat.com>
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Acked-by: NHerbert Xu <herbert@gondor.apana.org.au>
Tested-by: NCAI Qian <caiqian@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>