rxrpc: Absorb the rxkad security module

Absorb the rxkad security module into the af_rxrpc module so that there's
only one module file.  This avoids a circular dependency whereby rxkad pins
af_rxrpc and cached connections pin rxkad but can't be manually evicted
(they will expire eventually and cease pinning).

With this change, af_rxrpc can just be unloaded, despite having cached
connections.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rxrpc/Kconfig b/net/rxrpc/Kconfig
index 23dcef1..784c531 100644
--- a/net/rxrpc/Kconfig
+++ b/net/rxrpc/Kconfig
@@ -30,7 +30,7 @@
 
 
 config RXKAD
-	tristate "RxRPC Kerberos security"
+	bool "RxRPC Kerberos security"
 	depends on AF_RXRPC
 	select CRYPTO
 	select CRYPTO_MANAGER