vmalloc.h used to be included from include/net/inet_hashtables.h
but it is no longer the case.

Fixes: 095dc8e0 ("tcp: fix/cleanup inet_ehash_locks_alloc()")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Eric Dumazet <edumzet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>