qbus: remove wrong error messages

The existing code shows the "Bus '%s' is full" message even if name
is specified and different from bus->name (i.e. match=0).

The patch excludes unnecessary error message.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-id: 1366184940-13516-1-git-send-email-aik@ozlabs.ru
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>