mb/lenovo/t520/romstage: Remove unused includes

Tested - Lenovo t520 still builds fine with this patch.

Change-Id: I82492c071ca760f0790b992acbdb86021f470cfe
Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>
Reviewed-on: https://review.coreboot.org/c/30043
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

src/mainboard/lenovo/t520/romstage.c

@@ -16,18 +16,12 @@
  */
 
 #include <stdint.h>
-#include <string.h>
-#include <timestamp.h>
 #include <arch/byteorder.h>
 #include <arch/io.h>
 #include <device/pci_def.h>
-#include <device/pnp_def.h>
-#include <cpu/x86/lapic.h>
-#include <arch/acpi.h>
 #include <northbridge/intel/sandybridge/sandybridge.h>
 #include <northbridge/intel/sandybridge/raminit_native.h>
 #include <southbridge/intel/bd82x6x/pch.h>
-#include <southbridge/intel/common/gpio.h>
 #include <drivers/lenovo/hybrid_graphics/hybrid_graphics.h>
 #include <device/device.h>
 #include <device/pci.h>