tcp: Use ahash

This patch replaces uses of the long obsolete hash interface with
ahash.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 55be6ac..4c65ca1 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -1,3 +1,4 @@
+#include <linux/crypto.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>