x86: dynamically attach/detach CMT service for a guest

x86: dynamically attach/detach CMT service for a guest

Add hypervisor side support for dynamically attach and detach
Cache Monitoring Technology(CMT) services for a certain guest.

When attach CMT service for a guest, system will allocate an
RMID for it. When detach or guest is shutdown, the RMID will be
recycled for future use.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>