cpu/intel/common: Add CPU_INTEL_COMMON_TIMEBASE

To add a common tsc_freq_mhz() implementation, we need
to guard againts soc-specific duplicate definitions.

Change-Id: I37a34651d9e7d823ad5689d30739294358a97e31
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31341
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: David Guckian
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/cpu/intel/model_106cx/Kconfig

@@ -13,6 +13,7 @@ config CPU_INTEL_MODEL_106CX
 	select SUPPORT_CPU_UCODE_IN_CBFS
 	select SERIALIZED_SMM_INITIALIZATION
 	select CPU_INTEL_COMMON
+	select CPU_INTEL_COMMON_TIMEBASE
 
 if CPU_INTEL_MODEL_106CX