pci: hotplug: ibmphp: convert to kthread

Convert ibmphp to new kthread api

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>