soc/intel: convert XTAL frequency constant to Kconfig

This converts the constant for the XTAL frequency to a Kconfig option.

Change-Id: I1382dd274eeb9cb748f94c34f5d9a83880624c18
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46018
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/soc/intel/alderlake/cpu.c b/src/soc/intel/alderlake/cpu.c
index ee8051d..e6a21c1 100644
--- a/src/soc/intel/alderlake/cpu.c
+++ b/src/soc/intel/alderlake/cpu.c
@@ -111,15 +111,17 @@
 
 static void enable_pm_timer_emulation(void)
 {
-	/* ACPI PM timer emulation */
 	msr_t msr;
+
+	if (!CONFIG_CPU_XTAL_HZ)
+		return;
+
 	/*
 	 * The derived frequency is calculated as follows:
-	 * (CTC_FREQ * msr[63:32]) >> 32 = target frequency.
-	 * Back solve the multiplier so the 3.579545MHz ACPI timer
-	 * frequency is used.
+	 * (clock * msr[63:32]) >> 32 = target frequency.
+	 * Back solve the multiplier so the 3.579545MHz ACPI timer frequency is used.
 	 */
-	msr.hi = (3579545ULL << 32) / CTC_FREQ;
+	msr.hi = (3579545ULL << 32) / CONFIG_CPU_XTAL_HZ;
 	/* Set PM1 timer IO port and enable */
 	msr.lo = (EMULATE_DELAY_VALUE << EMULATE_DELAY_OFFSET_VALUE) |
 			EMULATE_PM_TMR_EN | (ACPI_BASE_ADDRESS + PM1_TMR);