cpu/intel: Use the common code to initialize the romstage timestamps

The initial timestamps are now pushed on the stack when entering the
romstage C code.

Tested on Asus P5QC.

Change-Id: I88e972caafff5c53d8e68e85415f920c7341b92d
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/30670
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/southbridge/intel/i82801gx/early_lpc.c

@@ -15,21 +15,10 @@
  */
 
 #include <arch/io.h>
-#include <timestamp.h>
-#include <cpu/x86/tsc.h>
 #include <console/console.h>
 #include <arch/acpi.h>
 #include "i82801gx.h"
 
-uint64_t get_initial_timestamp(void)
-{
-	tsc_t base_time = {
-		.lo = pci_read_config32(PCI_DEV(0, 0x00, 0), 0xdc),
-		.hi = pci_read_config32(PCI_DEV(0, 0x1f, 2), 0xd0)
-	};
-	return tsc_to_uint64(base_time);
-}
-
 int southbridge_detect_s3_resume(void)
 {
 	u32 reg32;