crypto: authenc - select CRYPTO_NULL

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 354bb69..ac7cc62 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -200,6 +200,7 @@
 	select CRYPTO_BLKCIPHER
 	select CRYPTO_MANAGER
 	select CRYPTO_HASH
+	select CRYPTO_NULL
 	help
 	  Authenc: Combined mode wrapper for IPsec.
 	  This is required for IPSec.