intel_rapl: abstract register address

MSR and MMIO RAPL interface have different sets of registers, thus the
RAPL register address should be obtained from interface specific
structure, i.e. struct rapl_if_private, instead.

Reviewed-by: Pandruvada, Srinivas <srinivas.pandruvada@intel.com>
Tested-by: Pandruvada, Srinivas <srinivas.pandruvada@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>