rxrpc: Drop channel number field from rxrpc_call struct

Drop the channel number (channel) field from the rxrpc_call struct to
reduce the size of the call struct.  The field is redundant: if the call is
attached to a connection, the channel can be obtained from there by AND'ing
with RXRPC_CHANNELMASK.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
index 896d844..6a5a17e 100644
--- a/net/rxrpc/conn_object.c
+++ b/net/rxrpc/conn_object.c
@@ -156,9 +156,10 @@
 void __rxrpc_disconnect_call(struct rxrpc_call *call)
 {
 	struct rxrpc_connection *conn = call->conn;
-	struct rxrpc_channel *chan = &conn->channels[call->channel];
+	struct rxrpc_channel *chan =
+		&conn->channels[call->cid & RXRPC_CHANNELMASK];
 
-	_enter("%d,%d", conn->debug_id, call->channel);
+	_enter("%d,%x", conn->debug_id, call->cid);
 
 	if (rcu_access_pointer(chan->call) == call) {
 		/* Save the result of the call so that we can repeat it if necessary