x86 romstage: Move stack just below RAMTOP

Placement of romstage stack in RAM was vulnerable for getting corrupted
by decompressed ramstage.

Change-Id: Ic032bd3e69f4ab8dab8e5932df39fab70aa3e769
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7096
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/cpu/intel/haswell/cache_as_ram.inc

@@ -18,7 +18,6 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include <cpu/x86/stack.h>
 #include <cpu/x86/mtrr.h>
 #include <cpu/x86/cache.h>
 #include <cpu/x86/post_code.h>

src/cpu/intel/haswell/romstage.c

@@ -25,7 +25,6 @@
 #include <cpu/x86/bist.h>
 #include <cpu/x86/msr.h>
 #include <cpu/x86/mtrr.h>
-#include <cpu/x86/stack.h>
 #include <lib.h>
 #include <timestamp.h>
 #include <arch/io.h>
@@ -85,7 +84,7 @@ static unsigned long choose_top_of_stack(void)
 	                                     ROMSTAGE_RAM_STACK_SIZE);
 	stack_top += ROMSTAGE_RAM_STACK_SIZE;
 #else
-	stack_top = ROMSTAGE_STACK;
+	stack_top = CONFIG_RAMTOP;
 #endif
 	return stack_top;
 }