powercap: intel_rapl: Support per Interface rapl_defaults

rapl_defaults is Interface specific.

Although current MSR and MMIO Interface share the same rapl_defaults,
new Interface like TPMI need its own rapl_defaults callbacks.

Save the rapl_defaults information in the Interface private structure.

No functional change.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wang Wendy <wendy.wang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>