x86: add COS information for each domain

x86: add COS information for each domain

In Xen's implementation, the CAT enforcement granularity is per domain.
Due to the length of CBM and the number of COS may be socket-different,
each domain has COS ID for each socket. The domain get COS=0 by default
and at runtime its COS is then allocated dynamically when user specifies
a CBM for the domain.

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>