x86: Implement per-cpu vector for xen hypervisor

x86: Implement per-cpu vector for xen hypervisor

Since Xen and Linux has big differece in code base, it
is very hard to port Linux's patch and apply it to Xen
directly, so this patch only adopts core logic of Linux,
and make it work for Xen.

Key changes:
1. vector allocation algorithm
2. all IRQ chips' set_affinity logic
3. IRQ migration when cpu hot remove.
4. Break assumptions which depend on global vector policy.

Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>