intel_rapl: abstract RAPL common code

Split intel_rapl.c to intel_rapl_common.c and intel_rapl_msr.c, where
intel_rapl_common.c contains the common code that can be used by both MSR
and MMIO interface.
intel_rapl_msr.c contains the implementation of RAPL MSR interface.

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>

drivers/powercap/Kconfig

@@ -16,14 +16,17 @@ menuconfig POWERCAP
 
 if POWERCAP
 # Client driver configurations go here.
+config INTEL_RAPL_CORE
+	tristate
+
 config INTEL_RAPL
-	tristate "Intel RAPL Support"
+	tristate "Intel RAPL Support via MSR Interface"
 	depends on X86 && IOSF_MBI
-	default n
+	select INTEL_RAPL_CORE
 	---help---
 	  This enables support for the Intel Running Average Power Limit (RAPL)
-	  technology which allows power limits to be enforced and monitored on
-	  modern Intel processors (Sandy Bridge and later).
+	  technology via MSR interface, which allows power limits to be enforced
+	  and monitored on modern Intel processors (Sandy Bridge and later).
 
 	  In RAPL, the platform level settings are divided into domains for
 	  fine grained control. These domains include processor package, DRAM

drivers/powercap/Makefile

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_POWERCAP)	+= powercap_sys.o
-obj-$(CONFIG_INTEL_RAPL) += intel_rapl.o
+obj-$(CONFIG_INTEL_RAPL_CORE) += intel_rapl_common.o
+obj-$(CONFIG_INTEL_RAPL) += intel_rapl_msr.o
 obj-$(CONFIG_IDLE_INJECT) += idle_inject.o