sched: rename v->cpu_affinity into v->cpu_hard_affinity

sched: rename v->cpu_affinity into v->cpu_hard_affinity

in order to distinguish it from the cpu_soft_affinity which will
be introduced a later commit ("xen: sched: introduce soft-affinity
and use it instead d->node-affinity").

This patch does not imply any functional change, it is basically
the result of something like the following:

 s/cpu_affinity/cpu_hard_affinity/g
 s/cpu_affinity_tmp/cpu_hard_affinity_tmp/g
 s/cpu_affinity_saved/cpu_hard_affinity_saved/g

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Reviewed-by: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>