[PATCH] Fix ESP SA loading (by default)

[Alexey Dobriyan <adobriyan@gmail.com>]

digest_null algorithm is now mandatory for ESP.

Steps to reproduce:

	kernel with CONFIG_CRYPTO_NULL=n

	#!/usr/sbin/setkey -f
	flush;
	spdflush;
	add 192.168.0.1 192.168.0.42 esp 15701 -E 3des-cbc "123456789012123456789012";

This will successfully create ESP SA.

Now, apply commit 38320c70d282be1997a5204c7c7fe14c3aa6bfaa aka
"[IPSEC]: Use crypto_aead and authenc in ESP" and ESP SAs won't be created.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 Ewwww, such a cool bug turned out to be configuration issue!

 And I was thinking why on earth why Debian 2.6.26 based kernel is OK,
 but 2.6.25-rc1 (!) fails. Ditto for minimalistic config for testing with KVM.
 Not mentioning Debian's gcc creating references to __ucmdhowitiscalled up
 and including to 2.6.18 and screwing bisection hard way.

 Now that I passed first IPsec tutorial, allow me to start netns XFRM work :^)

 net/ipv4/Kconfig |    1 +
 net/ipv6/Kconfig |    1 +
 2 files changed, 2 insertions(+)

--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -346,6 +346,7 @@ config INET_ESP
 	select CRYPTO_AUTHENC
 	select CRYPTO_HMAC
 	select CRYPTO_MD5
+	select CRYPTO_NULL
 	select CRYPTO_CBC
 	select CRYPTO_SHA1
 	select CRYPTO_DES
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -86,6 +86,7 @@ config INET6_ESP
 	select CRYPTO_AUTHENC
 	select CRYPTO_HMAC
 	select CRYPTO_MD5
+	select CRYPTO_NULL
 	select CRYPTO_CBC
 	select CRYPTO_SHA1
 	select CRYPTO_DES