staging/lustre: call set_cpus_allowed_ptr instead of set_cpus_allowed

set_cpus_allowed is not available with CONFIG_CPUMASK_OFFSTACK on.
We should call set_cpus_allowed_ptr instead.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>