soc/intel/common: Move PMC EPOC related code to Intel common code

Move PMC EPOC related code to intel/common/block because it is
generic for most Intel platforms and ADL, TGL & EHL use it.

Add a kconfig 'PMC_EPOC' to guard this common EPOC code.

The PMC EPOC register indicates which external crystal oscillator is
connected to the PCH.  This frequency is important for determining the
IP clock of internal PCH devices.

Signed-off-by: Lean Sheng Tan <lean.sheng.tan@intel.com>
Change-Id: Ib5fd3c4a648964678ee40ed0f60ca10fe7953f56
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55565
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/soc/intel/tigerlake/Kconfig

@@ -40,6 +40,7 @@ config CPU_SPECIFIC_OPTIONS
 	select REG_SCRIPT
 	select PMC_GLOBAL_RESET_ENABLE_LOCK
 	select PMC_LOW_POWER_MODE_PROGRAM
+	select PMC_EPOC
 	select SOC_INTEL_COMMON
 	select SOC_INTEL_COMMON_ACPI_WAKE_SOURCE
 	select SOC_INTEL_COMMON_BLOCK