intel car: Move pre-ram stack guard lower

SPD data alone consumes 0x400 of pre-ram stack, so the guard was
initially set too high, printing spurious "smashed stack detected"
messages at end of romstage.

Use the same stack size as haswell.

Change-Id: I24fff6228bc5207750a3c4bf8cf34e91cf35e716
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17501
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/cpu/intel/car/romstage.c

@@ -16,7 +16,7 @@
 #include <cpu/intel/romstage.h>
 #include <program_loading.h>
 
-#define DCACHE_RAM_ROMSTAGE_STACK_SIZE 0x800
+#define DCACHE_RAM_ROMSTAGE_STACK_SIZE 0x2000
 
 void * asmlinkage romstage_main(unsigned long bist)
 {