xfrm: make xfrm_algo.c a module

By making this a standalone config option (auto-selected as needed),
selecting CRYPTO from here rather than from XFRM (which is boolean)
allows the core crypto code to become a module again even when XFRM=y.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
index 6d08167..ce90b8d 100644
--- a/net/xfrm/Kconfig
+++ b/net/xfrm/Kconfig
@@ -3,12 +3,17 @@
 #
 config XFRM
        bool
-       select CRYPTO
        depends on NET
 
+config XFRM_ALGO
+	tristate
+	select XFRM
+	select CRYPTO
+
 config XFRM_USER
 	tristate "Transformation user configuration interface"
-	depends on INET && XFRM
+	depends on INET
+	select XFRM_ALGO
 	---help---
 	  Support for Transformation(XFRM) user configuration interface
 	  like IPsec used by native Linux tools.
@@ -48,13 +53,13 @@
 
 config XFRM_IPCOMP
 	tristate
-	select XFRM
+	select XFRM_ALGO
 	select CRYPTO
 	select CRYPTO_DEFLATE
 
 config NET_KEY
 	tristate "PF_KEY sockets"
-	select XFRM
+	select XFRM_ALGO
 	---help---
 	  PF_KEYv2 socket family, compatible to KAME ones.
 	  They are required if you are going to use IPsec tools ported