s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed

s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed

The guest's AP configuration is cleared when the mdev is removed, so
userspace must be notified that the AP configuration has changed. To this
end, this patch:

* Removes call to 'signal_guest_ap_cfg_changed()' function from the
  'vfio_ap_mdev_unset_kvm()' function because it has no affect given it is
  called after the mdev fd is closed.

* Adds call to 'signal_guest_ap_cfg_changed()' function to the
  'vfio_ap_mdev_request()' function to notify userspace that the guest's
  AP configuration has changed before signaling the request to remove the
  mdev.

Minor change - Fixed an indentation issue in function
'signal_guest_ap_cfg_changed()'

Fixes: 07d89045bffe ("s390/vfio-ap: Signal eventfd when guest AP configuration is changed")
Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
Reviewed-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304200812.54556-1-rreyes@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>