rxrpc: fix undefined behavior in rxrpc_mark_call_released

gcc -Wmaybe-initialized correctly points out a newly introduced bug
through which we can end up calling rxrpc_queue_call() for a dead
connection:

net/rxrpc/call_object.c: In function 'rxrpc_mark_call_released':
net/rxrpc/call_object.c:600:5: error: 'sched' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This sets the 'sched' variable to zero to restore the previous
behavior.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: f5c17aae ("rxrpc: Calls should only have one terminal state")
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/call_object.c

@@ -586,7 +586,7 @@ static void rxrpc_dead_call_expired(unsigned long _call)
  */
 static void rxrpc_mark_call_released(struct rxrpc_call *call)
 {
-	bool sched;
+	bool sched = false;
 
 	rxrpc_see_call(call);
 	write_lock(&call->state_lock);