driver core: fix possible missing of device probe

Inside bus_add_driver(), one device might be added(device_add()) into
the bus or probed which is triggered by deferred probe
just after completing of driver_attach() and before
'klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers)',
so the device won't be probed by this driver.

This patch moves the below line

	'klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers)'

before driver_attach() inside bus_add_driver() to fix the
problem.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>