ipsec: ipcomp - Merge IPComp implementations

This patch merges the IPv4/IPv6 IPComp implementations since most
of the code is identical.  As a result future enhancements will no
longer need to be duplicated.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/Kconfig b/net/xfrm/Kconfig
index 9201ef8..6d08167 100644
--- a/net/xfrm/Kconfig
+++ b/net/xfrm/Kconfig
@@ -46,6 +46,12 @@
 
 	  If unsure, say N.
 
+config XFRM_IPCOMP
+	tristate
+	select XFRM
+	select CRYPTO
+	select CRYPTO_DEFLATE
+
 config NET_KEY
 	tristate "PF_KEY sockets"
 	select XFRM