drivers/intel/fsp2_0: Use same stack with coreboot

This patch ensures to have same stack base for FSP and coreboot.

Feature added in FSP2.1
- Remove stack swapping from FSP.
- Stack will be shared between coreboot and FSP.

TEST=Build and boot FSP2.1 enable platform like dragonegg, iclrvp.
No car global variable corruption seen after enabling
this feature.

Change-Id: I673b4216d991d8ccad725c3931006a694184106c
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32079
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/intel/fsp2_0/memory_init.c

@@ -172,7 +172,7 @@ static enum cb_err setup_fsp_stack_frame(FSPM_ARCH_UPD *arch_upd,
 	 * top and does not reinitialize stack pointer.
 	 */
 	if (CONFIG(FSP_USES_CB_STACK)) {
-		arch_upd->StackBase = (void *)_car_stack_end;
+		arch_upd->StackBase = (void *)_car_stack_start;
 		arch_upd->StackSize = CONFIG_DCACHE_BSP_STACK_SIZE;
 		return CB_SUCCESS;
 	}