x86: intel: slimbootloader: Remove dead code

start.S does nothing and can be safely removed. Makefile is still being used
by the build system, so simply drop the rule from it.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Aiden Park <aiden.park@intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/board/intel/slimbootloader/Makefile b/board/intel/slimbootloader/Makefile
index fd8fa98..50330cc6 100644
--- a/board/intel/slimbootloader/Makefile
+++ b/board/intel/slimbootloader/Makefile
@@ -2,4 +2,4 @@
 #
 # Copyright (C) 2019 Intel Corporation <www.intel.com>
 
-obj-y	+= start.o slimbootloader.o
+obj-y	+= slimbootloader.o
diff --git a/board/intel/slimbootloader/start.S b/board/intel/slimbootloader/start.S
deleted file mode 100644
index 5c3f3df..0000000
--- a/board/intel/slimbootloader/start.S
+++ /dev/null
@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0+ */
-/*
- * Copyright (C) 2019 Intel Corporation <www.intel.com>
- */
-
-/* board early initialization */
-.globl early_board_init
-early_board_init:
-	jmp	early_board_init_ret