s390/ap: extend AP change bindings-complete uevent with counter

Userspace udev rules need an indication about the very first AP change
BINDINGS=complete uevent.

So now this uevent is extend with an additional key-value entry
COMPLETECOUNT=<counter>. The very first uevent will show counter=1 and
the following BINDINGS=complete uevents increase this counter by 1.

Here is an example how the very first BINDINGS=complete uevent
looks like:

  KERNEL[106.079510] change   /devices/ap (ap)
  ACTION=change
  DEVPATH=/devices/ap
  SUBSYSTEM=ap
  BINDINGS=complete
  COMPLETECOUNT=1
  SEQNUM=10686

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>