LU-8661 libcfs: handle padata_alloc() rename

LU-8661 libcfs: handle padata_alloc() rename

In upstream commit e6cc11707661770ca2bd4db4b0256d28f48e7541
the function padata_alloc() was renamed to padata_alloc_possible().

Change-Id: I6ad6a503af3c52fa3c64ef9b3452bd35d8490cd5
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: https://review.whamcloud.com/27491
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>