cpu/intel/common: add function to init cppc_config

This change adds a method to init a cppc_config structure in a way that
should ideally work across Intel processors that support EIST.

Change-Id: Ib767df63d796bd1f21e36bcf575cf912e09090a1
Signed-off-by: Matt Delco <delco@chromium.org>
Reviewed-on: https://review.coreboot.org/28068
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

src/cpu/intel/common/common.h

@@ -17,4 +17,12 @@
 
 void set_vmx(void);
 
+/*
+ * Init CPPC block with MSRs for Intel Enhanced Speed Step Technology.
+ * Version 2 is suggested--this function's implementation of version 3
+ * may have room for improvment.
+ */
+struct cppc_config;
+void cpu_init_cppc_config(struct cppc_config *config, u32 version);
+
 #endif