cpu/intel/car: Drop remains of setup_stack_and_mtrrs()

Platforms have moved to POSTCAR_STAGE=y.

Change-Id: I79c87e546805dbe0a4c28ed95f4d12666734eb79
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/30489
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/include/cpu/intel/romstage.h

@@ -5,23 +5,6 @@
 
 void mainboard_romstage_entry(unsigned long bist);
 
-/* romstage_main is called from the cache-as-ram assembly file. The return
- * value is the stack value to be used for romstage once cache-as-ram is
- * torn down. The following values are pushed onto the stack to setup the
- * MTRRs:
- *   +0: Number of MTRRs
- *   +4: MTRR base 0 31:0
- *   +8: MTRR base 0 63:32
- *  +12: MTRR mask 0 31:0
- *  +16: MTRR mask 0 63:32
- *  +20: MTRR base 1 31:0
- *  +24: MTRR base 1 63:32
- *  +28: MTRR mask 1 31:0
- *  +32: MTRR mask 1 63:32
- *  ...
- */
-void *setup_stack_and_mtrrs(void);
-
 void platform_enter_postcar(void);
 
 /* romstage_main is called from the cache-as-ram assembly file to prepare