They are 64K and result in order-4 allocations, even with SLUB.

Therefore, just like we always have for the deflate buffers, use
vmalloc.

Reported-by: Martin Jackson <mjackson220.list@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>