soc/intel: replace dt option PmTimerDisabled by Kconfig

Replace the dt option `PmTimerDisabled` with use of the Kconfig option
`USE_PM_ACPI_TIMER` for enabling/disabling the PM Timer.

A default value representing the prior devicetree value was added to the
boards system76/{lemp10,galp5,darp7}, so this change will not alter
behaviour.

Change-Id: If1811c6b98847b22272acfa35ca44f4fbca68947
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58016
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lance Zhao
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Tim Crawford <tcrawford@system76.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/soc/intel/alderlake/chip.h

@@ -286,7 +286,7 @@ struct soc_intel_alderlake_config {
 
 	/* Enable C6 DRAM */
 	uint8_t enable_c6dram;
-	uint8_t PmTimerDisabled;
+
 	/*
 	 * SerialIO device mode selection:
 	 * PchSerialIoDisabled,