ipv4+ipv6: Make INET*_ESP select CRYPTO_ECHAINIV

The ESP algorithms using CBC mode require echainiv. Hence INET*_ESP have
to select CRYPTO_ECHAINIV in order to work properly. This solves the
issues caused by a misconfiguration as described in [1].
The original approach, patching crypto/Kconfig was turned down by
Herbert Xu [2].

[1] https://lists.strongswan.org/pipermail/users/2015-December/009074.html
[2] http://marc.info/?l=linux-crypto-vger&m=145224655809562&w=2

Signed-off-by: Thomas Egerer <hakke_007@gmx.de>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index bb7dabe..40c8975 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -69,6 +69,7 @@
 	select CRYPTO_CBC
 	select CRYPTO_SHA1
 	select CRYPTO_DES
+	select CRYPTO_ECHAINIV
 	---help---
 	  Support for IPsec ESP.