intel/car: Use common TS_START_ROMSTAGE

This timestamp also got unintentionally removed from some
boards as they were transformed to use common romstage entry.

Change-Id: I12be278a674f9a2ea073b170a223c41c7fc01a94
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34970
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/skylake/romstage/romstage_fsp20.c

@@ -32,7 +32,6 @@
 #include <soc/pm.h>
 #include <soc/romstage.h>
 #include <string.h>
-#include <timestamp.h>
 #include <security/vboot/vboot_common.h>
 
 #include "../chip.h"
@@ -148,7 +147,6 @@ void mainboard_romstage_entry(void)
 	systemagent_early_init();
 
 	ps = pmc_get_power_state();
-	timestamp_add_now(TS_START_ROMSTAGE);
 	s3wake = pmc_fill_power_state(ps) == ACPI_S3;
 	fsp_memory_init(s3wake);
 	pmc_set_disb();