Driver core: add missing kset uevent

Driver core: add missing kset uevent

We get uevents for a bus/class going away, but not one registering.
Add the missing uevent in kset_register(), which will send an
event for a new bus/class. Suppress all unwanted uevents for bus
subdirectories like /bus/*/devices/, /bus/*/drivers/.

Now we get for module usbcore:
  add      /module/usbcore (module)
  add      /bus/usb (bus)
  add      /class/usb_host (class)
  add      /bus/usb/drivers/hub (drivers)
  add      /bus/usb/drivers/usb (drivers)
  remove   /bus/usb/drivers/usb (drivers)
  remove   /bus/usb/drivers/hub (drivers)
  remove   /class/usb_host (class)
  remove   /bus/usb (bus)
  remove   /module/usbcore (module)

instead of:
  add      /module/usbcore (module)
  add      /bus/usb/drivers/hub (drivers)
  add      /bus/usb/drivers/usb (drivers)
  remove   /bus/usb/drivers/usb (drivers)
  remove   /bus/usb/drivers/hub (drivers)
  remove   /class/usb_host (class)
  remove   /bus/usb/drivers (bus)
  remove   /bus/usb/devices (bus)
  remove   /bus/usb (bus)
  remove   /module/usbcore (module)

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>