acpiphp: stop bus device before acpi_bus_trim

Contrary to PCI bridge hot-add, we need to follow the sequence below
for PCI bridge hot-removal.

  (1) Stop devices (detach drivers, remove from the global list, etc.)
  (2) Unbind ACPI node from the devices (remove the _PRT entries)
  (3) Remove devices (remove from the device list, etc.)

This patch fixes acpiphp driver to follow above sequence for P2P
bridge hot-removal.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: MUNEDA Takahiro <muneda.takahiro@jp.fujitsu.com>
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>