resctrl is the defacto Linux ABI for SoC resource partitioning features.
To support it on another architecture, it needs to be abstracted from
the features provided by Intel RDT and AMD PQoS, and moved to /fs/.
Split struct rdt_domain up too. Move everything that that is particular
to resctrl into a new header file. resctrl code paths touching a 'hw'
struct indicates where an abstraction is needed.