xen/sched: move per cpu scheduler private data into struct sched_resource

xen/sched: move per cpu scheduler private data into struct sched_resource

This prepares support of larger scheduling granularities, e.g. core
scheduling.

While at it move sched_has_urgent_vcpu() from include/asm-x86/cpuidle.h
into sched.h removing the need for including sched-if.h in cpuidle.h.
For that purpose remobe urgent_count from the scheduler private data
and make it a plain percpu variable.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Dario Faggioli <dfaggioli@suse.com>