net: allow GFP_HIGHMEM in __vmalloc()

We forgot to use __GFP_HIGHMEM in several __vmalloc() calls.

In ceph, add the missing flag.

In fib_trie.c, xfrm_hash.c and request_sock.c, using vzalloc() is
cleaner and allows using HIGHMEM pages as well.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 200eb53..0f28034 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -365,7 +365,7 @@
 	if (size <= PAGE_SIZE)
 		return kzalloc(size, GFP_KERNEL);
 	else
-		return __vmalloc(size, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
+		return vzalloc(size);
 }
 
 static void __tnode_vfree(struct work_struct *arg)