svc: Add an svc transport class

The transport class (svc_xprt_class) represents a type of transport, e.g.
udp, tcp, rdma.  A transport class has a unique name and a set of transport
operations kept in the svc_xprt_ops structure.

A transport class can be dynamically registered and unregisterd. The
svc_xprt_class represents the module that implements the transport
type and keeps reference counts on the module to avoid unloading while
there are active users.

The endpoint (svc_xprt) is a generic, transport independent endpoint that can
be used to send and receive data for an RPC service. It inherits it's
operations from the transport class.

A transport driver module registers and unregisters itself with svc sunrpc
by calling svc_reg_xprt_class, and svc_unreg_xprt_class respectively.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
index 3912cf1..092fcfa 100644
--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -21,6 +21,7 @@
 #define RPCDBG_SCHED		0x0040
 #define RPCDBG_TRANS		0x0080
 #define RPCDBG_SVCSOCK		0x0100
+#define RPCDBG_SVCXPRT		0x0100
 #define RPCDBG_SVCDSP		0x0200
 #define RPCDBG_MISC		0x0400
 #define RPCDBG_CACHE		0x0800